chore(package): update webpack-dev-server to version 3.7.1

Closes #22

Author: greenkeeper[bot]

package.json

@@ -41,7 +41,7 @@
     "electron-debug": "^1.1.0",
     "electron-webpack": "1.9.0",
     "webpack": "^3.6.0",
-    "webpack-dev-server": "^2.9.2",
+    "webpack-dev-server": "^3.7.1",
     "xo": "^0.18.2"
   },
   "xo": {