chore(package): update webpack-dev-server to version 3.1.9

Closes #17

Author: greenkeeper[bot]

package.json

@@ -57,7 +57,7 @@
     "react-addons-test-utils": "^15.4.2",
     "semantic-release": "^6.3.2",
     "webpack": "^2.3.0",
-    "webpack-dev-server": "^2.2.1"
+    "webpack-dev-server": "^3.1.9"
   },
   "config": {
     "commitizen": {