Add complete callback when fetching from cache

Hey,
I noticed that the `complete` callback was not being fired when fetching from cache, and it's something I use in my code. Perhaps this was intentional? If not, I'm submitting a PR to add it, along with tests.

I think my tests catch everything, and I ran grunt with success, but I'm a jasmine newbie so it's possible I missed something.

If this is useful to anyone else, feel free to accept it, if not I'll just use it in my own stuff :)

Cheers