Futurize nonzero: renamed __nonzero__ to __bool__
Futurize nonzero: renamed __nonzero__ to __bool__

http://python-future.org/compatible_idioms.html?#nonzero
Signed-off-by: Dan Yeaw <2591e5f46f28d303f9dc027d475a5c60d8dea17a@yeaw.me>

amolenaar/gaphas