SRS Setup on schedule, minor tests added

- Added CeleryBeat schedule for SRS.(Once a minute)
- Added a "Refresh" button to Home page, forces an SRS update for the
user.
- Fixed a minor bug in all_srs which caused the logging to always say
there were 0 reviews.
- Fixed a major bug where it would also query reviews that had been
previously flagged for review.
- Force-review check returns the total number of reviews to be done
after the check.
TODO: write some js that fills in the Reviews button based on the
force_srs ajax response.