Allow projects to be quickly added from GitHub repository data

As you can now sign in to the app using GitHub, I've added a feature to allow you to quickly add a new project for deployment using repositories that you have access to on GitHub.

Note that this also includes your own private repositories and private repositories of organizations that you are a member of.

If you have any feedback or suggested code changes, let me know. Some additional refactoring will be done to extract the GitHub API request logic from the ProjectController.

![screen shot 2015-01-01 at 16 14 51](https://cloud.githubusercontent.com/assets/5972864/5592640/bb4f6aaa-91d1-11e4-95e7-676cf205aca8.png)

![screen shot 2015-01-01 at 16 15 16](https://cloud.githubusercontent.com/assets/5972864/5592641/bf906254-91d1-11e4-8704-d659675f087e.png)