Merge pull request #647 from syuilo/greenkeeper/webpack-3.4.1

chore(package): update webpack to version 3.4.1

package.json

@@ -89,7 +89,7 @@
     "uglify-es": "3.0.24",
     "uglify-es-webpack-plugin": "0.0.3",
     "uglify-js": "git+https://github.com/mishoo/UglifyJS2.git#harmony",
-    "webpack": "3.3.0"
+    "webpack": "3.4.1"
   },
   "dependencies": {
     "accesses": "2.5.0",