Merge pull request #1424 from mozilla/greenkeeper/webpack-3.4.1

Update webpack to the latest version 🚀

package.json

@@ -62,7 +62,7 @@
     "request": "2.81.0",
     "sinon": "2.4.0",
     "tar": "3.1.7",
-    "webpack": "3.3.0",
+    "webpack": "3.4.1",
     "webpack-dev-server": "2.6.1"
   },
   "dependencies": {