Modernization

Hey there! Thanks for making this code available on GitHub, it's helped me out on a project recently. I spent some time updating the code and figured I'd contribute it back. It's a fairly big change, so I understand if it's not what you're looking for. In that case I'd probably create my own repo with credit to yourself for the original code.

## Changes

- Update visual style for Xcode 5's project editor
- Refactor code for ARC and with modern Objective-C syntax
- Increase target OS to 10.7 Lion (minimum for weak references)
- Update README for Xcode 5 and with a screenshot preview

Either way, I think it would also be good if you added a [MIT license file](https://help.github.com/articles/open-source-licensing#how-can-i-go-back-through-my-public-repositories-and-give-them-licenses) with your name in the copyright. I'd like to add this repo to [CocoaPods](http://cocoapods.org/) and their pod repo requires license files.

Thanks!