Django-birdbath

- Improve compatibility with older Django versions

- Update Faker version
- Remove un-used faker dependency
- Update README
- Add BaseModelAnonymiser class

- Batch errors
- Add check for an 'ALLOWS_ANONYMISATION' variable
- Add configuration and Makefile for pypi
- Don't fail checks if birdbath tables don't exist
- Django system check if birdbath hasn't executed

Initial version