chore(package): update webpack to version 4.40.1

Closes #3

Author: greenkeeper[bot]

package.json

@@ -45,6 +45,6 @@
     "jest": "^21.2.1",
     "title-case": "^2.1.1",
     "uglifyjs-webpack-plugin": "^1.0.1",
-    "webpack": "^3.8.1"
+    "webpack": "^4.40.1"
   }
 }