Revamped how api file uploads work and are tested.  The "correct" methods seem
to fail utterly thanks to stupid character encoding nightmares.  Nothing I
did could convince Rails that my image upload was binary not ASCII.  Grumble.
So screw it, just separated out testing case completely, and grab everything
raw straight from the tester via header fields.  I swear, Rails has become a
nightmare if you have the temerity to do anything they in their ultimate
wisdom don't sanction with their fancy clever automagical techniques.  If we
don't want to send data via JSON or HTTP form (in which case everything would
just magically work), there's no longer any support whatsoever for direct
access to raw post data.  Not that I'm bitter about wasting a whole day on
this or anything.