chore(package): update webpack to version 2.4.0

Closes #7

https://greenkeeper.io/

Author: greenkeeper[bot]

package.json

@@ -48,7 +48,7 @@
     "phantomjs-prebuilt": "^2.1.3",
     "semantic-release": "^6.3.2",
     "sia": "0.0.9",
-    "webpack": "^1.13.0"
+    "webpack": "^2.4.0"
   },
   "config": {
     "commitizen": {