Check for primary key on object before checking if it's empty. Fixes special case for South datamigrations.
Bumped version
Merge branch 'master' of github.com:bradjasper/django-jsonfield
Fix signature of six.with_metaclass.
Merge pull request #54 from carljm/six-1.4-compat

Fix signature of six.with_metaclass.
bump version to 0.9.19
Merge conflicts