* Move serve_multiple, remove stop_events, fix tests
Moves serve_multiple out of the app, removes stop_event (adds a
deprecation warning, but it also wasn't doing anything) fixes
multiprocessing tests so that they don't freeze pytest's runner.
Other notes:
Also moves around some imports so that they are better optimized as
well.
* Re-add in stop_event, maybe it wasn't so bad!
* Get rid of unused warnings import
