Please update Pod repository

[markzyu]

Currently, pod install GTMAppAuth will only install version 0.5.0 which yields compilation errors if used together with "AppAuth" and Swift 3.

[elsesiy]

I second that, the oid repo has made great improvements in terms of the swift developer experience.

[aaroncrespo]

@WilliamDenniss This issue prevents Podspecs. from linking to this Pod as a dependency and breaks builds. The only fix is a fork. If this project is not support the Readme should point to the preferred Google Auth library and all the other sample projects referencing it should be updated.