fix(package): update webpack-dev-middleware to version 2.0.0

Closes #31

Author: greenkeeper[bot]

package.json

@@ -55,7 +55,7 @@
     "sanitize.css": "4.1.0",
     "style-loader": "0.13.1",
     "webpack": "1.13.3",
-    "webpack-dev-middleware": "1.8.4",
+    "webpack-dev-middleware": "2.0.0",
     "webpack-hot-middleware": "2.13.1",
     "webpack-merge": "2.1.1"
   },