chore(package): update rollup-plugin-babel to version 4.0.2

Closes #16

Author: greenkeeper[bot]

package.json

@@ -57,7 +57,7 @@
     "mocha": "^5.0.4",
     "parse-json": "^4.0.0",
     "rollup": "^0.60.0",
-    "rollup-plugin-babel": "^3.0.3",
+    "rollup-plugin-babel": "^4.0.2",
     "semantic-release": "^15.0.0",
     "sinon": "^6.0.0",
     "sinon-stub-promise": "^4.0.0",