Kill jobs on teardown

[thinkerbot]

Probably need to think about this more, but if you start background jobs then they will hang without something like this:

  jobs -p | xargs kill

Bonus points to kill politely, then kill -9 if they don't exit in a reasonable time.

[thinkerbot]

This may be extremely non-trivial. One of the problems I've run into is that you can kill but then it's hard to know if you should kill -9 later. See here.