Merge branch 'release/0.4' into develop
fix natural key (must use uuid.hex) and add missing model manager

also added fixtures, as is more stable than json. currently is using django-whatever, but can be updated in fixtures.py without impacting tests.
Merge pull request #4 from saxix/feature/fix_natural_key_dumpdata

fix natural key (must use uuid.hex) and add missing model manager
bump 0.4.1
Merge branch 'release/0.4.1'