Django-jalali

Fixed
- Fix chaining filters problem

Fixed
- Fixed `jDateTimeField` problem with `auto_now_add` when tz enable (124)

Fixed
- Fix Django Jalali javascipt files loading when Django Jquery file loaded first

Changed
- Add Python 3.9 support
- Drop Python 3.4 support
- Drop Django < 2.2 support

Changed
- Improved handling timezone

Fixed
- Fix serialization of django_jalali.db.models