chore(package): update webpack to version 4.2.0

Closes #203

package.json

@@ -95,7 +95,7 @@
     "typescript": "^2.6.1",
     "uglifyjs-webpack-plugin": "^1.0.1",
     "underscore-template-loader": "^0.8.0",
-    "webpack": "^3.5.5",
+    "webpack": "^4.2.0",
     "webpack-dev-server": "2.7.1",
     "webpack-merge": "^4.1.1",
     "webpack-visualizer-plugin": "^0.1.11"