CocoaPods support

Added a working [Cocoapods](http://cocoapods.org) [podspec](http://docs.cocoapods.org/specification.html).

Could you confirm the [license](https://help.github.com/articles/open-source-licensing) and create a tag?

Also it would be cool if you added some [collaborators](https://help.github.com/articles/how-do-i-add-a-collaborator) to keep alive this project.