chore(package): update webpack to version 4.1.0

Closes #118

Author: greenkeeper[bot]

package.json

@@ -141,7 +141,7 @@
     "vue-style-loader": "^4.0.0",
     "vue-template-compiler": "^2.4.4",
     "vue-template-es2015-loader": "^2.1.2",
-    "webpack": "^3.6.0",
+    "webpack": "^4.1.0",
     "webpack-dev-middleware": "^2.0.0",
     "webpack-dev-server": "^2.9.1",
     "webpack-hot-middleware": "^2.19.1",