chore(package): update webpack to version 4.7.0

Closes #36

Author: greenkeeper[bot]

package.json

@@ -66,7 +66,7 @@
     "nyc": "11.4.1",
     "standard-version": "4.3.0",
     "text-loader": "0.0.1",
-    "webpack": "3.11.0",
+    "webpack": "4.7.0",
     "xo": "0.18.2"
   }
 }