initial code commit

simple middleware and management command to run a test server that
exposes an endpoint to reset the server/database between tests.

includes docs, tests, travis-ci integration.
Thanks for catching this. This is left over from when this function was a context manager. Except that the context manager didn't clean up when an assert failed (wtf?!), so I had to split the context manager to a pre- and post-save function. Oh well.