Uses iOS 7 Base 64 Methods Instead if NSData+Base64

iOS 7, finally, introduced native Base 64 handling, so why not use it?

This does require the deployment target for both iOS and OS X to be the latest version, so I created a new version of the podspec. Also, set build only active architectures to YES so that this and the tests build on Xcode 5.

Tested with the Authentication example app.

Since this is the first time I've worked with Podspecs, I may have missed something. Let me know.