chore(package): update html-webpack-plugin to version 4.2.1

Closes #40

Author: greenkeeper[bot]

package.json

@@ -44,7 +44,7 @@
     "eslint-watch": "^3.0.1",
     "express": "4.15.2",
     "extract-text-webpack-plugin": "^2.1.0",
-    "html-webpack-plugin": "^2.28.0",
+    "html-webpack-plugin": "^4.2.1",
     "jsdom": "^10.0.0",
     "json-schema-faker": "^0.4.1",
     "json-server": "^0.10.0",