Two major changes:
1) db_query now wraps all table names in {}s (including the install script)
2) ECv3.3 has a thing where you can make any node a product in your store. Previously we didn't support that too well. This version does.
Bugfix for node-add. We were calling _skipcart_getvars with a non-integer NID value. Whoops. Also removed some debugging calls that were still in there.