Tahi-project/tahi — pull request #566 by neo-tahi (2014-11-03 22:11:08+00:00)
Title: Single Streaming [DO NOT MERGE]

### References
* https://www.pivotaltracker.com/story/show/81129650

### Major Changes
* Example of how paper event_stream actions can be pushed down the User channel, rather than the Paper channel
* Addition of a `Accessibility` class which answers the question: "What users have access to this resource (i.e., paper)?"
* `Accessibility` class ensures that security is maintained by using the matching resource policy (i.e, PaperPolicy) to determine if the user should have access to the data
* Policy has a notion of `connected_users` which is the superset of all users that have access to its resource

### Important Notes
* This is simply a step toward allowing an easier, larger refactor of `EventStream`. Baby steps.