Merge pull request #1675 from mozilla/greenkeeper/webpack-hot-middleware-2.16.0

Update webpack-hot-middleware to the latest version 🚀

package.json

@@ -261,6 +261,6 @@
     "webpack": "1.14.0",
     "webpack-dev-middleware": "1.10.0",
     "webpack-dev-server": "2.3.0",
-    "webpack-hot-middleware": "2.15.0"
+    "webpack-hot-middleware": "2.16.0"
   }
 }