Add Google as an authentication option.

Expand on Samson's authentication options to include Google too.

This is what you'll get (after you follow the readme to populate your .env file):

![screen shot 2014-05-30 at 12 03 23 pm](https://cloud.githubusercontent.com/assets/58188/3126324/9cc7a530-e79e-11e3-9c61-39082e16825c.png)

![screen shot 2014-05-30 at 11 57 17 am](https://cloud.githubusercontent.com/assets/58188/3126316/87bcbc16-e79e-11e3-87ea-cb0dae6bf6c5.png)

Happy Friday @jwswj and @steved555 :smile: