fix(package): update webpack to version 2.2.1 (#938)

https://greenkeeper.io/

package.json

@@ -79,7 +79,7 @@
     "styled-jsx": "0.5.2",
     "url": "0.11.0",
     "uuid": "3.0.1",
-    "webpack": "2.2.0-rc.6",
+    "webpack": "2.2.1",
     "webpack-dev-middleware": "1.9.0",
     "webpack-hot-middleware": "2.16.1",
     "write-file-webpack-plugin": "3.4.2"