chore(package): update webpack to version 4.12.1

Closes #271

Author: greenkeeper[bot]

package.json

@@ -91,7 +91,7 @@
     "vue": "^2.4.4",
     "vue-loader": "^13.0.5",
     "vue-template-compiler": "^2.4.4",
-    "webpack": "^3.6.0",
+    "webpack": "^4.12.1",
     "webpack-bundle-analyzer": "^2.9.0",
     "webpack-dashboard": "^1.0.0-5",
     "webpack-dev-server": "^2.9.1",