End of week 7 commits

Includes the following:
1. Moving Video rating formatting from the model to a decorator
2. Writing a sign up service object and corresponding test for the service object and moving relevant tests out of the users controller into the service object tests.
I'm a bit confused about which version of bootstrap I'm using. I tried using success in a previous exercise and it stopped working. Also if I update version of bootstrap then I believe I can use classes like "span6" rather than "col-sm-6". Could you advise please,