Add support for CocoaPods

HI,

I'd like to use your library and import it using [CocoaPods](https://github.com/CocoaPods/CocoaPods) so I created a podspec file.
A few things:
* I had to change the structure of folders to support subspecs and their dependencies
* There was no tag version that I could point the source repo to so I specified a commit for now. It would be better to have a tag instead.
* I left the version to `0.0.1` as the default

Thanks