Add Notification#commit_count

The wall display was suffering from a rather nasty n+1 query.
Because notifications regularly want to know the number of commits
they have, just have a counter that is calculated in
Notification.create_from_payload.
Initial move towards Github authentication
Adding OmniAuth testing information

James Bond is our user for our tests, just because he has a really cool
name to test against.
Initial login from Github with controller specs
Set current_user to be the Github user

If the session[:github_user] exists, use that for the current user.
Annotate the user model
Users are able to log in and out via Github
Fix tpyo
Save the oauth token from github on the User
Move OmniAuth user decisions into it's own class
GitHub, not twitter

Copy/paste is hard.
Provider and uid should not be NULL, just empty
Ensure that users where they are logging in
Add naive notice alerts to the page