Add paper to dashboard upon collaboration changes

References:
* https://www.pivotaltracker.com/story/show/77045390

Major changes:
* event stream now contains a user stream that can listen for specific events for a specific user
* generalizes event stream destroy action to work for any model (not just task)
* adds ability to refresh a user's event channels

--- AC + CT

This was an intentional change.  Passing in the actual model looks and feels more natural.  It allows us to easily pass different types of models into event stream channels without worrying about building up a hash first.