Replace third-party libraries with CocoaPods

PR for #1

[CocoaPods](http://cocoapods.org/) allows for much more flexible third-party library management, as whenever projects are updated, you only have to do a `pod update` command instead of having to reimport the source into the project. I couldn't add `BMAddRemoveButton`, `BMArrowView`, and `BMInfinitePager` in this manner since they're your personal projects, but if you decide to extract them into separate open-source projects, we can make Podspecs for them too.

Let me know what you think!