PhoneGap 3 plugin compatible

Few notes:

1. Arbitrarily I changed the class to `org.apache.cordova.plugin` - there's an argument for this not being in either cordova space, nor the phonegap namespace.
2. Removed the demo link - probably could be added back with an updated link
3. I've no clue if this is backward compatible with PhoneGap 2.x
4. Just noticed the README.md needs to update the git repo to yours instead of mine

Otherwise, it all works.