chore(package): update webpack-dev-middleware to version 1.8.1

https://greenkeeper.io/

package.json

@@ -72,7 +72,7 @@
     "style-loader": "0.13.1",
     "url-loader": "0.5.7",
     "webpack": "2.1.0-beta.21",
-    "webpack-dev-middleware": "1.6.1",
+    "webpack-dev-middleware": "1.8.1",
     "webpack-hot-middleware": "2.12.2",
     "yargs": "5.0.0"
   },