Some changes

Hi 

I have chosen your library for the work I am doing at Foursquare, but I have made some changes to support what we needed out of it. I have tried not to make them foursquare specific in case you are interested in pulling the changes in.

Some things I have added.

- ARC compatible
- You can add any UIView as a token
- Some extra callback methods
- errr others I cannot remember (check commits)

You probably want to look through the commits before you decide to pull them in as I may have taken it a bit too in being specific for our use case? (I hope not)

Thanks

Andy