Drf-tracking

- Fixes installation issue for Mysql backend support 29
- Updates TravisCI Tox testing to run against MySQL, PostgreSQL, & SQLite backends 29

NOTE: This version refactors drf-tracking's initial migration file and is likely backwards incompatible with current installations. Upgrade with caution.

Thanks to jameshiew

This release addresses:
- Support for MySQL backend 19 , 25
- Refactored fields used on the `APIRequestLogAdmin` class 21
- Updates to docs and package metadata to align requirements for DRF, Django, & Python versions 30
- `PrefetchUserManager` class query performance enhancement 23

**NOTE:** This version refactors drf-tracking's initial migration file and is likely backwards incompatible with current installations. Upgrade with caution.

Thanks to ( jameshiew , zatarus , null-none , abriemme )

APIRequestLog.remote_addr` is now X_FORWARDED_FOR by default, REMOTE_ADDR if not. This closes PR 14 and PR 15. Thanks yrchen!

Add MySQL support, and refactor to not override DRF error message when user is inactive. Thanks mayankkapoor!