chore(package): update @types/webpack to version 4.1.0

Closes #24

Author: greenkeeper[bot]

package.json

@@ -71,7 +71,7 @@
     "@types/jasmine": "^2.5.47",
     "@types/karma": "^0.13.35",
     "@types/node": "^8.0.13",
-    "@types/webpack": "^3.0.4",
+    "@types/webpack": "^4.1.0",
     "@types/webpack-env": "^1.13.0",
     "angular2-template-loader": "^0.6.2",
     "awesome-typescript-loader": "^3.1.3",