Added a lazySubmit callback for firing accept()

I needed the ability to explicitly control when the data was committed back to the original scope (after an $http callback), so I added a callback to lazySubmit.

http://jsbin.com/IWoPINU/3/edit

Long-term, it would be convenient to also be able to take the return value of the finalSubmit and use it as a gauge for success if a callback is not specified.