User auth saga

1st part
- Added Omniauth gem and configuration
- Created model Sessions
- Refactoring RepositoryService to acknowledge private repositories

2nd part
- Added User Model
- Added Octokit for Github API easy access 
- Added Dashboard page
- Added concept of current user session 
- Home page now has a link to Github auth, which redirects to the User Dashboard
- The Dashboard currently lists all the user repos and all their branches
- The tests are failing because of the major refactoring going on 

3rd part
- Added Foundation 
- Refactoring of the Home, Dashboard and Report page
- Refactoring of the engine classes
- 2 tests are still failing