chore(package): update webpack to version 4.29.1

Closes #11

Author: greenkeeper[bot]

package.json

@@ -42,7 +42,7 @@
     "ts-helper": "0.0.1",
     "ts-loader": "^2.3.1",
     "typescript": "^2.4.2",
-    "webpack": "^3.3.0",
+    "webpack": "^4.29.1",
     "webpack-dev-middleware": "^1.5.1",
     "webpack-dev-server": "^2.6.0",
     "webpack-notifier": "^1.3.0"