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

I do not believe that these arguments can be factored out because the subscribe block expects them and we needed the payload arg.  We factored them out everywhere else we could since they weren't being used and underscored them here to emphasized that they aren't actually used.