Refactored utils tests.

Moved things into their own test module.  A single module for all the
tests was getting crowded.  This was in preparation for some extra
tests, but I didn't end up writing them.  Still, I think the split is
good.
New system for tracking hit counts

Implemented a new way to track hit counts.  This one doesn't use
redit, it just inserts into a DB table.

The old way had a fairly complicated system for adding counts:
  - It would create a task to insert the count
  - The task would update a redis field
  - Every so often another task would migrate that field to the
    regular DB

The new system is:
  - Insert a row for the hit using INSERT DELAYED
  - Every day we count rows in the hit table for yesterday and
    aggregate them to the per-day table
  - At the start of the month we sum up counts in the per-day table
    for last month and move them to the per-month table.
  - We then delete hits older than 24 hours and per-day counts older
    than 1 month.

I think the new system should perform better than the old system.
Using INSERT DELAYED should be just as fast, if not faster than
scheduling a task.  The total number of rows in the 3 tables should be
reasonable (right now we have like 23 million rows in the per-day
table, which makes queries slow).  We avoid scheduling a task for each
hit, which was resulting in something like tens of thousands of tasks
per hour.
Switched to using the new hitcounting system

Made the video view counts use the statistic.hitcounts.video_hits
object.

Made video.get_views() use the video hits, rather than widget views.

Dropped the subtitles fetched count and the widget views count, we
decided those aren't really needed.

Removed the old hit count migration task and replaced it with the new
one.
fixed JS syntax error
Removed a couple count columns from videos/languages

We're not using these anymore
Changed post edit subtitles permissions check (#483)
Fixed AttributeError in indexing code
Updated feedback link for the new editor
Order video actions by creation date (#812)

Before we were ordering them by ID, which seems like it should be the
same, but results in the wild prove otherwise.  Added an index on
created so that the queries will be as fast.
Fixed widget download link (#473)

Also fixed the view code in case the lang_pk is not present
Remove permissions checks for activity tabs (#869)
Display video view counts again
Bump integration repo (#800)
Don't use INSERT DELAYED

It doesn't work on InnoDB tables.  I think it should be fast anyways,
since InnoDB uses a write-ahead log.
update test data fixtures
remove screenshot and outdated test
configured for postfix
updated docker setup
updated docker setup for worker
updated docker setup for email