adding tvOS support in UIKit extensions

[romainbiard]

Hello,
I just had to extend the compiler check to be able to work with tvOS.
Great pod BTW, loving it !

Thanks,
Romain

[jflinter]

This isn't sufficient to add tvOS support. At the bare minimum,

• You need to actually add a scheme to the xcodeproj to make sure that the project actually builds for tvOS.
• This scheme must be built and tested during travis builds.
• The .podspec must be updated to indicate that tvOS is supported.

[romainbiard]

Ok since tvOS support was already in the podspec I assumed it was only this class which needs a quick update. Give me a few minute to reopen a new PR