Modernize to curent build standards

Migrate to pbr, flake8 and hacking. Clean up hacking warnings. Rename
requirements files. Remove cruft from tox.ini.

Change-Id: Ide78ad47de7f275240f729a2bc02745063b084ac
Reviewed-on: https://review.openstack.org/31439
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins