Update documentation for how to get access to the documentation.
Update documentation for how to get access to the documentation.

Change-Id: Ibfdba4a5ef72fb3293faca55768af20d8220e740

googlesamples/android-play-games-in-motion,maheshg6486/android-play-games-in-motion,AdamRLukaitis/android-play-games-in-motion