chore(package): update webpack-dev-server to version 3.1.0

Closes #272

Author: greenkeeper[bot]

package.json

@@ -94,7 +94,7 @@
     "webpack": "^3.6.0",
     "webpack-bundle-analyzer": "^2.9.0",
     "webpack-dashboard": "^1.0.0-5",
-    "webpack-dev-server": "^2.9.1",
+    "webpack-dev-server": "^3.1.0",
     "webpack-merge": "^4.1.0",
     "yarn-or-npm": "^2.0.4"
   },