Add event stream utility class for Backbonization of EventSource.
Add a notification model and a progress subtype for it
Add notification stream implementation on the server
Merge remote-tracking branch 'origin/master' into event-stream
Fix web client tests hanging
Use UTC timestamps in model layer

MongoDB (sensibly) always operates in UTC, and we should too for
consistency. Clients will be responsible for coercing timestamps
to the user's timezone when rendering them.
FIX ALL OF THE TESTS!!! (>'-')>  <('-'<)
Do not try to sort text search results by text score.
Don't try to depend on an undefined ordering.
Add a progress context manager

This is used to rate-limit progress update writes to the database
and provide convenient semantics for callers to easily manage
progress.
Merge remote-tracking branch 'origin/master' into event-stream

Conflicts:
	clients/web/test/spec/collectionSpec.js
Make sure SSE channels close when server is shutting down
Do sort by text score, but only if result count isn't too high
Add some basic search help
Add a recent version of six as a requirement.
I refactored how settings and their defaults are done so that the default is in exactly one place.  Also, as I was adding a setting, our check for cyclomatic complexity prohibited having the chain of if-elif for validation, so I refactored validating settings to call subfunctions.  I also added methods to get the default value of a setting and to check if a setting was using its default value (which is distinct from just having the default value).
Moving six to dev-dependencies.
Merge pull request #358 from girder/add-six

Add a recent version of six as a requirement.
Make text score sort threshold a constant variable.
Fix python style.