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.
Same with this, there should be a space between the method name and the argument. Parentheses around the argument are optional, and the space should be omitted if parentheses are used.