Fix column creation in make_update_script_for_model.
Fix column creation in make_update_script_for_model.

Generating the script needs internal API updates:
https://code.google.com/p/sqlalchemy-migrate/issues/detail?id=113

Getting the script to run needs the new columns defined:
https://code.google.com/p/sqlalchemy-migrate/issues/detail?id=123

Table metadata represents the former state and does not contain
the columns being added.
openstack/sqlalchemy-migrate,emonty/sqlalchemy-migrate,openstack/sqlalchemy-migrate,stackforge/sqlalchemy-migrate,emontyoncrack/wookie18,rcherrueau/sqlalchemy-migrate,dannon/sqlalchemy-migrate,rcherrueau/sqlalchemy-migrate,andras-tim/sqlalchemy-migrate