SDK updates 

Changes:
-Many style changes to match Objective-C coding style
-Fix broken JSON key for clickthrough_url
-Added a public bool to enable/disable test mode (more convenient, like Admob)
-Basic validation of the returned JSON (type checking, return nil if missing critical fields)
-Minor bug fixes
-Added Cocoapod spec (we use it internally)

If you do merge this request, be sure to change the pod spec to point to your fork instead of ours (and tag the commit "0.0.2"). Then the Podspec could be submitted to Cocoapods. 

This would be better as multiple pull requests (one for each feature), but this is the actual version we are using and so is informational only.