Upgrade webpack-dev-server

* Fixes #480
* See https://www.npmjs.com/advisories/725

Author: junowilderness

package.json

@@ -51,7 +51,7 @@
     "webpack": "^4.20.0",
     "webpack-chunk-hash": "^0.6.0",
     "webpack-cli": "^3.0.0",
-    "webpack-dev-server": "^3.1.4",
+    "webpack-dev-server": "^3.1.14",
     "webpack-manifest-plugin": "^2.0.2",
     "webpack-sources": "^1.3.0",
     "yargs": "^8.0.1"