Bump bootstrap-sass from 3.3.5.1 to 3.4.1

Bumps [bootstrap-sass](https://github.com/twbs/bootstrap-sass) from 3.3.5.1 to 3.4.1.
- [Release notes](https://github.com/twbs/bootstrap-sass/releases)
- [Changelog](https://github.com/twbs/bootstrap-sass/blob/master/CHANGELOG.md)
- [Commits](https://github.com/twbs/bootstrap-sass/commits/v3.4.1)

---
updated-dependencies:
- dependency-name: bootstrap-sass
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Gemfile

@@ -20,7 +20,7 @@ gem 'middleman-breadcrumbs',           '~> 0.3.3'
 
 # Assets
 gem 'bourbon',                         '~> 3.2.3', require: false
-gem 'bootstrap-sass',                  '~> 3.3.5.1', require: false
+gem 'bootstrap-sass',                  '~> 3.4.1', require: false
 gem 'jquery-middleman',                '~> 3.0.4'
 gem 'middleman-trailing_slashes',	     '~> 0.0.1'
 gem 'middleman-alias',                 '~> 0.0'

Gemfile.lock

@@ -8,11 +8,11 @@ GEM
       thread_safe (~> 0.1)
       tzinfo (~> 1.1)
     addressable (2.3.8)
-    autoprefixer-rails (6.3.6)
-      execjs
-    bootstrap-sass (3.3.5.1)
-      autoprefixer-rails (>= 5.0.0.1)
-      sass (>= 3.3.0)
+    autoprefixer-rails (10.4.19.0)
+      execjs (~> 2)
+    bootstrap-sass (3.4.1)
+      autoprefixer-rails (>= 5.2.1)
+      sassc (>= 2.0.0)
     bourbon (3.2.4)
       sass (~> 3.2)
       thor
@@ -41,7 +41,7 @@ GEM
       http_parser.rb (~> 0.6.0)
     erubis (2.7.0)
     eventmachine (1.2.0.1)
-    execjs (2.6.0)
+    execjs (2.9.1)
     exifr (1.2.4)
     fastimage (1.9.0)
       addressable (~> 2.3.5)
@@ -153,7 +153,9 @@ GEM
     redcarpet (3.2.3)
     ref (2.0.0)
     rouge (1.10.1)
-    sass (3.4.22)
+    sass (3.4.25)
+    sassc (2.4.0)
+      ffi (~> 1.9)
     slim (3.0.6)
       temple (~> 0.7.3)
       tilt (>= 1.3.3, < 2.1)
@@ -187,7 +189,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  bootstrap-sass (~> 3.3.5.1)
+  bootstrap-sass (~> 3.4.1)
   bourbon (~> 3.2.3)
   builder (~> 3.2.2)
   fastimage (~> 1.6)