diff --git a/Pipfile.lock b/Pipfile.lock
index 3c7f4d8..0577be0 100644
--- a/Pipfile.lock
+++ b/Pipfile.lock
@@ -22,42 +22,66 @@
         },
         "pillow": {
             "hashes": [
-                "sha256:01bb0a34f1a6689b138c0089d670ae2e8f886d2666a9b2f2019031abdea673c4",
-                "sha256:07872f1d8421db5a3fe770f7480835e5e90fddb58f36c216d4a2ac0d594de474",
-                "sha256:1022f8f6dc3c5b0dcf928f1c49ba2ac73051f576af100d57776e2b65c1f76a8d",
-                "sha256:14415e9e28410232370615dbde0cf0a00e526f522f665460344a5b96973a3086",
-                "sha256:172acfaf00434a28dddfe592d83f2980e22e63c769ff4a448ddf7b7a38ffd165",
-                "sha256:1c5e3c36f02c815766ae9dd91899b1c5b4652f2a37b7a51609f3bd467c0f11fb",
-                "sha256:292f2aa1ae5c5c1451cb4b558addb88c257411d3fd71c6cf45562911baffc979",
-                "sha256:2a40d7d4b17db87f5b9a1efc0aff56000e1d0d5ece415090c102aafa0ccbe858",
-                "sha256:2f0d7034d5faae9a8d1019d152ede924f653df2ce77d3bba4ce62cd21b5f94ae",
-                "sha256:33fdbd4f5608c852d97264f9d2e3b54e9e9959083d008145175b86100b275e5b",
-                "sha256:3b13d89d97b551e02549d1f0edf22bed6acfd6fd2e888cd1e9a953bf215f0e81",
-                "sha256:3e759bcc03d6f39bc751e56d86bc87252b9a21c689a27c5ed753717a87d53a5b",
-                "sha256:3ec87bd1248b23a2e4e19e774367fbe30fddc73913edc5f9b37470624f55dc1f",
-                "sha256:436b0a2dd9fe3f7aa6a444af6bdf53c1eb8f5ced9ea3ef104daa83f0ea18e7bc",
-                "sha256:43b3c859912e8bf754b3c5142df624794b18eb7ae07cfeddc917e1a9406a3ef2",
-                "sha256:4fe74636ee71c57a7f65d7b21a9f127d842b4fb75511e5d256ace258826eb352",
-                "sha256:59445af66b59cc39530b4f810776928d75e95f41e945f0c32a3de4aceb93c15d",
-                "sha256:69da5b1d7102a61ce9b45deb2920a2012d52fd8f4201495ea9411d0071b0ec22",
-                "sha256:7094bbdecb95ebe53166e4c12cf5e28310c2b550b08c07c5dc15433898e2238e",
-                "sha256:8211cac9bf10461f9e33fe9a3af6c5131f3fdd0d10672afc2abb2c70cf95c5ca",
-                "sha256:8cf77e458bd996dc85455f10fe443c0c946f5b13253773439bcbec08aa1aebc2",
-                "sha256:924fc33cb4acaf6267b8ca3b8f1922620d57a28470d5e4f49672cea9a841eb08",
-                "sha256:99ce3333b40b7a4435e0a18baad468d44ab118a4b1da0af0a888893d03253f1d",
-                "sha256:a7d690b2c5f7e4a932374615fedceb1e305d2dd5363c1de15961725fe10e7d16",
-                "sha256:b9af590adc1e46898a1276527f3cfe2da8048ae43fbbf9b1bf9395f6c99d9b47",
-                "sha256:bb18422ad00c1fecc731d06592e99c3be2c634da19e26942ba2f13d805005cf2",
-                "sha256:c10af40ee2f1a99e1ae755ab1f773916e8bca3364029a042cd9161c400416bd8",
-                "sha256:c143c409e7bc1db784471fe9d0bf95f37c4458e879ad84cfae640cb74ee11a26",
-                "sha256:c448d2b335e21951416a30cd48d35588d122a912d5fe9e41900afacecc7d21a1",
-                "sha256:d30f30c044bdc0ab8f3924e1eeaac87e0ff8a27e87369c5cac4064b6ec78fd83",
-                "sha256:df534e64d4f3e84e8f1e1a37da3f541555d947c1c1c09b32178537f0f243f69d",
-                "sha256:f6fc18f9c9c7959bf58e6faf801d14fafb6d4717faaf6f79a68c8bb2a13dcf20",
-                "sha256:ff83dfeb04c98bb3e7948f876c17513a34e9a19fd92e292288649164924c1b39"
+                "sha256:0412516dcc9de9b0a1e0ae25a280015809de8270f134cc2c1e32c4eeb397cf30",
+                "sha256:04835e68ef12904bc3e1fd002b33eea0779320d4346082bd5b24bec12ad9c3e9",
+                "sha256:06d1adaa284696785375fa80a6a8eb309be722cf4ef8949518beb34487a3df71",
+                "sha256:085a90a99404b859a4b6c3daa42afde17cb3ad3115e44a75f0d7b4a32f06a6c9",
+                "sha256:0b9911ec70731711c3b6ebcde26caea620cbdd9dcb73c67b0730c8817f24711b",
+                "sha256:10e00f7336780ca7d3653cf3ac26f068fa11b5a96894ea29a64d3dc4b810d630",
+                "sha256:11c27e74bab423eb3c9232d97553111cc0be81b74b47165f07ebfdd29d825875",
+                "sha256:11eb7f98165d56042545c9e6db3ce394ed8b45089a67124298f0473b29cb60b2",
+                "sha256:13654b521fb98abdecec105ea3fb5ba863d1548c9b58831dd5105bb3873569f1",
+                "sha256:15ccb81a6ffc57ea0137f9f3ac2737ffa1d11f786244d719639df17476d399a7",
+                "sha256:18a07a683805d32826c09acfce44a90bf474e6a66ce482b1c7fcd3757d588df3",
+                "sha256:19ec4cfe4b961edc249b0e04b5618666c23a83bc35842dea2bfd5dfa0157f81b",
+                "sha256:1c3ff00110835bdda2b1e2b07f4a2548a39744bb7de5946dc8e95517c4fb2ca6",
+                "sha256:27a330bf7014ee034046db43ccbb05c766aa9e70b8d6c5260bfc38d73103b0ba",
+                "sha256:2b11c9d310a3522b0fd3c35667914271f570576a0e387701f370eb39d45f08a4",
+                "sha256:2c661542c6f71dfd9dc82d9d29a8386287e82813b0375b3a02983feac69ef864",
+                "sha256:2cde7a4d3687f21cffdf5bb171172070bb95e02af448c4c8b2f223d783214056",
+                "sha256:2d5e9dc0bf1b5d9048a94c48d0813b6c96fccfa4ccf276d9c36308840f40c228",
+                "sha256:2f23b2d3079522fdf3c09de6517f625f7a964f916c956527bed805ac043799b8",
+                "sha256:35d27687f027ad25a8d0ef45dd5208ef044c588003cdcedf05afb00dbc5c2deb",
+                "sha256:35d409030bf3bd05fa66fb5fdedc39c521b397f61ad04309c90444e893d05f7d",
+                "sha256:4326ea1e2722f3dc00ed77c36d3b5354b8fb7399fb59230249ea6d59cbed90da",
+                "sha256:4abc247b31a98f29e5224f2d31ef15f86a71f79c7f4d2ac345a5d551d6393073",
+                "sha256:4d89a2e9219a526401015153c0e9dd48319ea6ab9fe3b066a20aa9aee23d9fd3",
+                "sha256:4e59e99fd680e2b8b11bbd463f3c9450ab799305d5f2bafb74fefba6ac058616",
+                "sha256:548794f99ff52a73a156771a0402f5e1c35285bd981046a502d7e4793e8facaa",
+                "sha256:56fd98c8294f57636084f4b076b75f86c57b2a63a8410c0cd172bc93695ee979",
+                "sha256:59697568a0455764a094585b2551fd76bfd6b959c9f92d4bdec9d0e14616303a",
+                "sha256:6bff50ba9891be0a004ef48828e012babaaf7da204d81ab9be37480b9020a82b",
+                "sha256:6cb3dd7f23b044b0737317f892d399f9e2f0b3a02b22b2c692851fb8120d82c6",
+                "sha256:7dbfbc0020aa1d9bc1b0b8bcf255a7d73f4ad0336f8fd2533fcc54a4ccfb9441",
+                "sha256:838eb85de6d9307c19c655c726f8d13b8b646f144ca6b3771fa62b711ebf7624",
+                "sha256:8b68f565a4175e12e68ca900af8910e8fe48aaa48fd3ca853494f384e11c8bcd",
+                "sha256:8f284dc1695caf71a74f24993b7c7473d77bc760be45f776a2c2f4e04c170550",
+                "sha256:963ebdc5365d748185fdb06daf2ac758116deecb2277ec5ae98139f93844bc09",
+                "sha256:a048dad5ed6ad1fad338c02c609b862dfaa921fcd065d747194a6805f91f2196",
+                "sha256:a1bd983c565f92779be456ece2479840ec39d386007cd4ae83382646293d681b",
+                "sha256:a66566f8a22561fc1a88dc87606c69b84fa9ce724f99522cf922c801ec68f5c1",
+                "sha256:bcb04ff12e79b28be6c9988f275e7ab69f01cc2ba319fb3114f87817bb7c74b6",
+                "sha256:bd24054aaf21e70a51e2a2a5ed1183560d3a69e6f9594a4bfe360a46f94eba83",
+                "sha256:be25cb93442c6d2f8702c599b51184bd3ccd83adebd08886b682173e09ef0c3f",
+                "sha256:c691b26283c3a31594683217d746f1dad59a7ae1d4cfc24626d7a064a11197d4",
+                "sha256:cc9d0dec711c914ed500f1d0d3822868760954dce98dfb0b7382a854aee55d19",
+                "sha256:ce2e5e04bb86da6187f96d7bab3f93a7877830981b37f0287dd6479e27a10341",
+                "sha256:ce651ca46d0202c302a535d3047c55a0131a720cf554a578fc1b8a2aff0e7d96",
+                "sha256:d0c8ebbfd439c37624db98f3877d9ed12c137cadd99dde2d2eae0dab0bbfc355",
+                "sha256:d675a876b295afa114ca8bf42d7f86b5fb1298e1b6bb9a24405a3f6c8338811c",
+                "sha256:dde3f3ed8d00c72631bc19cbfff8ad3b6215062a5eed402381ad365f82f0c18c",
+                "sha256:e5a31c07cea5edbaeb4bdba6f2b87db7d3dc0f446f379d907e51cc70ea375629",
+                "sha256:f514c2717012859ccb349c97862568fdc0479aad85b0270d6b5a6509dbc142e2",
+                "sha256:fc0db32f7223b094964e71729c0361f93db43664dd1ec86d3df217853cedda87",
+                "sha256:fd4fd83aa912d7b89b4b4a1580d30e2a4242f3936882a3f433586e5ab97ed0d5",
+                "sha256:feb5db446e96bfecfec078b943cc07744cc759893cef045aa8b8b6d6aaa8274e"
             ],
             "index": "pypi",
-            "version": "==8.1.1"
+            "version": "==8.3.2"
+        },
+        "sanitized-package": {
+            "editable": true,
+            "path": "."
         }
     },
     "develop": {
@@ -66,14 +90,16 @@
                 "sha256:6d1784dea7c0c8d4a5172b6c620f40b6e4cbfdf96d783691f2e1302a7b88e197",
                 "sha256:ae70396ad1a434f9c7046fd2dd196fc04b12f9e91ffb859164193be8b6168a7a"
             ],
+            "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3'",
             "version": "==1.4.0"
         },
         "attrs": {
             "hashes": [
-                "sha256:31b2eced602aa8423c2aea9c76a724617ed67cf9513173fd3a4f03e3a929c7e6",
-                "sha256:832aa3cde19744e49938b91fea06d69ecb9e649c93ba974535d08ad92164f700"
+                "sha256:149e90d6d8ac20db7a955ad60cf0e6881a3f20d37096140088356da6c716b0b1",
+                "sha256:ef6aaac3ca6cd92904cdd0d83f629a15f18053ec84e6432106f7a4d04ae4f5fb"
             ],
-            "version": "==20.3.0"
+            "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3, 3.4'",
+            "version": "==21.2.0"
         },
         "coverage": {
             "hashes": [
@@ -130,35 +156,39 @@
                 "sha256:f0b278ce10936db1a37e6954e15a3730bea96a0997c26d7fee88e6c396c2086d",
                 "sha256:f11642dddbb0253cc8853254301b51390ba0081750a8ac03f20ea8103f0c56b6"
             ],
+            "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3, 3.4' and python_version < '4'",
             "version": "==5.5"
         },
         "importlib-metadata": {
             "hashes": [
-                "sha256:742add720a20d0467df2f444ae41704000f50e1234f46174b51f9c6031a1bd71",
-                "sha256:b74159469b464a99cb8cc3e21973e4d96e05d3024d337313fedb618a6e86e6f4"
+                "sha256:b618b6d2d5ffa2f16add5697cf57a46c76a56229b0ed1c438322e4e95645bd15",
+                "sha256:f284b3e11256ad1e5d03ab86bb2ccd6f5339688ff17a4d797a0fe7df326f23b1"
             ],
             "markers": "python_version < '3.8'",
-            "version": "==3.7.3"
+            "version": "==4.8.1"
         },
         "more-itertools": {
             "hashes": [
-                "sha256:5652a9ac72209ed7df8d9c15daf4e1aa0e3d2ccd3c87f8265a0673cd9cbc9ced",
-                "sha256:c5d6da9ca3ff65220c3bfd2a8db06d698f05d4d2b9be57e1deb2be5a45019713"
+                "sha256:70401259e46e216056367a0a6034ee3d3f95e0bf59d3aa6a4eb77837171ed996",
+                "sha256:8c746e0d09871661520da4f1241ba6b908dc903839733c8203b552cffaf173bd"
             ],
-            "version": "==8.7.0"
+            "markers": "python_version >= '3.5'",
+            "version": "==8.9.0"
         },
         "pluggy": {
             "hashes": [
-                "sha256:15b2acde666561e1298d71b523007ed7364de07029219b604cf808bfa1c765b0",
-                "sha256:966c145cd83c96502c3c3868f50408687b38434af77734af1e9ca461a4081d2d"
+                "sha256:4224373bacce55f955a878bf9cfa763c1e360858e330072059e10bad68531159",
+                "sha256:74134bbf457f031a36d68416e1509f34bd5ccc019f0bcc952c7b909d06b37bd3"
             ],
-            "version": "==0.13.1"
+            "markers": "python_version >= '3.6'",
+            "version": "==1.0.0"
         },
         "py": {
             "hashes": [
                 "sha256:21b81bda15b66ef5e1a777a21c4dcd9c20ad3efd0b3f817e7a809035269e1bd3",
                 "sha256:3b80836aa6d1feeaa108e046da6423ab8f6ceda6468545ae8d02d9d58d18818a"
             ],
+            "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3'",
             "version": "==1.10.0"
         },
         "pytest": {
@@ -179,26 +209,28 @@
         },
         "six": {
             "hashes": [
-                "sha256:30639c035cdb23534cd4aa2dd52c3bf48f06e5f4a941509c8bafd8ce11080259",
-                "sha256:8b74bedcbbbaca38ff6d7491d76f2b06b3592611af620f8426e82dddb04a5ced"
+                "sha256:1e61c37477a1626458e36f7b1d82aa5c9b094fa4802892072e49de9c60c4c926",
+                "sha256:8abb2f1d86890a2dfb989f9a77cfcfd3e47c2a354b01111771326f8aa26e0254"
             ],
-            "version": "==1.15.0"
+            "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3'",
+            "version": "==1.16.0"
         },
         "typing-extensions": {
             "hashes": [
-                "sha256:7cb407020f00f7bfc3cb3e7881628838e69d8f3fcab2f64742a5e76b2f841918",
-                "sha256:99d4073b617d30288f569d3f13d2bd7548c3a7e4c8de87db09a9d29bb3a4a60c",
-                "sha256:dafc7639cde7f1b6e1acc0f457842a83e722ccca8eef5270af2d74792619a89f"
+                "sha256:49f75d16ff11f1cd258e1b988ccff82a3ca5570217d7ad8c5f48205dd99a677e",
+                "sha256:d8226d10bc02a29bcc81df19a26e56a9647f8b0a6d4a83924139f4a8b01f17b7",
+                "sha256:f1d25edafde516b146ecd0613dabcc61409817af4766fbbcfb8d1ad4ec441a34"
             ],
             "markers": "python_version < '3.8'",
-            "version": "==3.7.4.3"
+            "version": "==3.10.0.2"
         },
         "zipp": {
             "hashes": [
-                "sha256:3607921face881ba3e026887d8150cca609d517579abe052ac81fc5aeffdbd76",
-                "sha256:51cb66cc54621609dd593d1787f286ee42a5c0adbb4b29abea5a63edc3e03098"
+                "sha256:957cfda87797e389580cb8b9e3870841ca991e2125350677b2ca83a0e99390a3",
+                "sha256:f5812b1e007e48cff63449a5e9f4e7ebea716b4111f9c4f9a645f91d579bf0c4"
             ],
-            "version": "==3.4.1"
+            "markers": "python_version >= '3.6'",
+            "version": "==3.5.0"
         }
     }
 }
diff --git a/requirements-dev.txt b/requirements-dev.txt
index 97d6d8f..3ce4eb8 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -1,13 +1,26 @@
+#
+# These requirements were autogenerated by pipenv
+# To regenerate from the project's Pipfile, run:
+#
+#    pipenv lock --requirements --dev
+#
+
+# Note: in pipenv 2020.x, "--dev" changed to emit both default and development
+# requirements. To emit only development requirements, pass "--dev-only".
+
 -i https://pypi.org/simple/
-atomicwrites==1.4.0
-attrs==20.3.0
-coverage==5.5
-importlib-metadata==3.7.3 ; python_version < '3.8'
-more-itertools==8.7.0
-pluggy==0.13.1
-py==1.10.0
+-e .
+-e .
+atomicwrites==1.4.0; python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3'
+attrs==21.2.0; python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3, 3.4'
+coverage==5.5; python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3, 3.4' and python_version < '4'
+importlib-metadata==4.8.1; python_version < '3.8'
+more-itertools==8.9.0; python_version >= '3.5'
+pillow==8.3.2
+pluggy==1.0.0; python_version >= '3.6'
+py==1.10.0; python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3'
 pytest-cov==2.6.1
 pytest==4.1.1
-six==1.15.0
-typing-extensions==3.7.4.3 ; python_version < '3.8'
-zipp==3.4.1
+six==1.16.0; python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3'
+typing-extensions==3.10.0.2; python_version < '3.8'
+zipp==3.5.0; python_version >= '3.6'