@orta => DSL subspec for analytics

- [x] Figure out some CocoaPods craziness
- [x] First Pass
- [x] Completing implementation for screens
- [x] Events
- [x] Testing
- [x] OS X Support

Reference: http://albertodebortoli.github.io/blog/2014/03/25/an-aspect-oriented-approach-programming-to-ios-analytics/

Closes #73.