chore(package): update webpack-dev-server to version 3.8.1

Closes #52

Author: greenkeeper[bot]

Diff for: package.json

@@ -43,7 +43,7 @@
     "uglifyjs-webpack-plugin": "^2.1.3",
     "webpack": "4.32.0",
     "webpack-cli": "3.3.2",
-    "webpack-dev-server": "3.4.1"
+    "webpack-dev-server": "3.8.1"
   },
   "dependencies": {
     "@uirouter/angularjs": "1.0.22",