An refactor project create with owner

Just saw a quick opportunity to improve this, and thought I'd share. IMHO, the Project#set_owner method is unnecessary. If there's some need for it that the tests do not cover, then you might consider at least removing the project as an argument to the method, since this would work just as well:

```ruby
def set_owner(user)
  self.owner = user
end
```

Cheers! :beers: