Added a reference to the view that fires stickitChange events

It can be useful when handling stickitChange events to know which view handled that change in cases where two or more views are monitoring the same model.
Merge branch 'master' of github.com:underbluewaters/backbone.stickit into underbluewaters-master

* 'master' of github.com:underbluewaters/backbone.stickit:
  Added a reference to the view that fires stickitChange events