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.
Again space is there as far as I can see :-) I have in Ruby generally omitted parentheses, because the ruby way seems to be only add these when you really need to or it makes the code much cleaner to read, otherwise it is just clutter right ? I come from a C++ background where parentheses are mandatory, so it's a serious change of habit for me ;-)