Adds podspec

Spec has subspecs so things like gamekit backports can be ignored.

Moves backported includes into their own header used with the aggregate
pod subspec so they're not automatically included when adding the pch
and some subspecs arent used which would result in a linking error.
Cleaned up the conditional import

Cleans up the method used to include specific subspec for cocoapods
Merge pull request #1 from tapi/Podspec

Podspec