chore(package): update webpack to version 4.1.1

Closes #23

Author: greenkeeper[bot]

package.json

@@ -104,7 +104,7 @@
     "tslint": "^5.2.0",
     "typescript": "^2.3.2",
     "upver": "^1.0.0",
-    "webpack": "^3.3.0",
+    "webpack": "^4.1.1",
     "webpack-angular-externals": "^1.0.2",
     "webpack-rxjs-externals": "^1.0.0",
     "zone.js": "^0.8.10"