Django-flags

- Add support for Django 3.1 [71](https://github.com/cfpb/django-flags/pull/71)

- Remove Django 1.11 support and cleanup for 5.0.0 release 68
- Add validator support to condition registration and FlagStateForm 61
- Raise MiddlewareNotUsed in deprecated FlagConditionsMiddleware 66
- Remove unsupported django-debug-toolbar version 64
- Add support for Django 3.0 58
- Deprecate middleware, instead lazily cache flags 60
- Clarify docs for anonymous condition 54

See https://cfpb.github.io/django-flags/releasenotes/ for more.

- Set `FLAGS_STATE_LOGGING` to `False` by default 50
- Update index.md 49

- Remove "optional" from state string language 48

- Move optional/required condition filtering back to check_state() 47
- Fix minor typo 46

- Use clearer language for booleans with required conditions 45