PEP8 tidy for test/orm/test_versioning.py
Fix support for two phase commit in pg8000 dialect

The postgresql base dialect has problems with two-phase commit because
there isn't a standard way of handling autocommit in DBAPI. This commit
modifies the pg8000 dialect to use the DBAPI tpc extension, which is
supported by pg8000 as of version 1.9.11.
PEP8 tidy for test/orm/test_transaction.py
pg8000 passing test/orm/test_query.py
PEP8 tidy of test/orm/test_query.py
Remove requirement for manytomany_nonpassive

Removed the non_updating_cascade requirement from
test_manytomany_nonpassive. This is because setting
passive_updates=False in a relationship should work on *all* dialects.
PEP8 tidy for test/orm/test_naturalpks.py
Opened test_self_referential for pg8000

The test orm/test_froms.py test_self_referential works with pg8000 now,
so I've opened it up.
PEP8 tidy of test/orm/test_froms.py
Fixes for pg8000 for test/orm/test_dynamic.py
PEP8 tidy of test/orm/test_dynamic.py
Merge remote-tracking branch 'origin/pr/117' into pg8000
- more pg8000 tests passing