Django-pg-returning

Testing
1. Using GitHub Actions instead of Travis CI

Requirements
1. Removed python 2.7 from testing
2. Removed `six` and `pytz` from requirements
3. `typing` library is now installed for python before 3.5 only
4. Require `psycopg2-binary` instead of `psycopg2`

Features
Added create_returning method to Manager and QuerySet

Bug fixes
Fixed [issue 20](20): save_returning() failed when inserting data

Tests
Added tests on basic Model.save() method to ensure it has not been broken

Bug fixes
1. Fixed django 3.1 [compatibility issue](https://github.com/M1ha-Shvn/django-pg-returning/issues/19)

Testing

Bug fixes
1. Fixed django 3.0 compatibility

Testing
1. Replaced Python 3.4 with python 3.8 testing
2. Replaced PostgreSQL 9.3 with PostgreSQL 12 testing

Bug fixes
1. Fixed a library update bug with UpdateReturningModel, if model has been pickled without library required field

Bug fixes
1. Fixed [issue of using non-id primary key](https://github.com/M1hacka/django-pg-returning/issues/16) by [Marco Falcioni](https://github.com/marcofalcioni)