chore(package): update webpack to version 4.22.0

Closes #27

Author: greenkeeper[bot]

package.json

@@ -39,7 +39,7 @@
     "react-dom": "^15.3.0",
     "sinon": "^2.0.0",
     "standard-version": "^4.0.0",
-    "webpack": "^1.13.1"
+    "webpack": "^4.22.0"
   },
   "dependencies": {
     "commander": "^2.9.0",