Moved GHViewTestCase.[hm] from Classes to Classes-iOS

Gabriel,

I moved ```GHViewTestCase.h``` and ```GHViewTestCase.m``` from ```Classes``` to ```Classes-iOS```. They certainly are iOS-specific, and I couldn't see why they would be in the common ```Classes``` directory.

(In addition, the location of these files was causing some issues with building the OSX version using CocoaPod)

I'm happy to stand corrected if there is a good reason for them being there ;-)

Matthew