chore(package): update webpack-manifest-plugin to version 2.1.2

Closes #53

Author: greenkeeper[bot]

package.json

@@ -72,7 +72,7 @@
     "webpack": "^1.13.0",
     "webpack-dev-middleware": "^1.6.1",
     "webpack-hot-middleware": "^2.10.0",
-    "webpack-manifest-plugin": "^1.0.1",
+    "webpack-manifest-plugin": "^2.1.2",
     "yargs": "^6.5.0"
   },
   "dependencies": {