Apply class native-key-bindings to allow copy

As was found out in https://github.com/rgbkrk/atom-script/pull/74#issuecomment-38523402, applying class `native-key-bindings` allows for things like cmd-c/copy to work.

![copypastatest](https://f.cloud.github.com/assets/836375/2507803/ca8b4470-b3c5-11e3-810b-789844b2e7c9.gif)