Bundle ios_webkit_debug_proxy for OS X. Fixes #37.

This includes the iOS proxy into the add-on for OS X.

The process to start things like iOS from WebIDE is still crazy, but I'm actively fixing up how the WebIDE API to this add-on separately.
I was afraid you would say that :)
That's certainly fine for now and perhaps @erikvold can tell us if there is a way to test if the add-on is running via jpm on runtime.