Don't destroy the traceback by reraising, just use plain 'raise'.
Save the clustoversion version id# when adding a row, and use it for the rest of the transaction.  Prevents deadlocks.
Make counter creation and incrementing transactionally isolated.
Forcing sqlalchemy to 0.6.4
Clear SESSION.transaction_version when the transaction is committed.

Without this, later transactions end up on a weird version, especially
if other programs have been running their own transactions in the meantime.
Nuke versioning, all unit tests pass

Cherry-picked from synack/clusto:no_versioning

Manually merged conflicts:

	src/clusto/schema.py
	src/clusto/test/base/versioningtests.py