- proof of concept for parallel testing
Merge branch 'master' into xdist_poc
- use a template database for PG so extensions get created automatically
- rework the exclusions system to have much better support for compound
rules, better message formatting
Merge branch 'master' into xdist_poc

Conflicts:
	lib/sqlalchemy/engine/url.py
- scale up for mysql, sqlite
fix paren here
Merge branch 'master' into xdist_poc
- reorganize tox options
- add support for tags, including include/exclude support.
simplify tox again now that we can exclude tests more easily