Changing the sign-in process for iOS to match our more modern flow
Revert last commit -- added wrong file.

This reverts commit c93f1414504a2c12260c7247ccd0f23d37223488.
Updated sign-in progress to no longer use deprecated methods
Merge pull request #172 from playgameservices/iosfixes

Updating the sign-in process to use non-deprecated methods. Got approval from Damien. :)