wubloader/common
Mike Lang 997c1242b2 get_best_segments: Let other things run
get_best_segments can sometimes take a very long time,
we don't want to stop other work from happening while it's ongoing.
So we ask gevent to run other things until there's no other work to do,
then we do one hour, then check back with gevent again.

In combination with the performance improvements, this should mean we don't block
other things from running for more than a few hundred ms at most.
..
common get_best_segments: Let other things run
setup.py parse_segment_path: Use datetime.strptime instead of dateutil.parser