* 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
By using the builtin pytest skips we can identify that the tests are still there but are being currently skipped.
Will update later to remove the skips once we figure out why they freeze with pytest (I experienced this same issue with multiprocessing when testing start/stop events).
