Django-clickhouse

Testing
1. Added docker testing environment
2. Moved testing from TravisCI to GitHub Actions

Docs
1. Added development section

Dependencies
1. Optimized dependency installation: removed `six`; `pytz` and `typing` are now installed in old python versions only; `psycopg2` is replaced with `psycopg2-binary` in test requireements.

Bug fixes
1. Fixed compatibility with celery JSON serializer
2. Fixed django database connection leaking in child threads during sync

Logging
1. Added debug logs for sync process

Testing
1. Added django 3.1 to Travis tests

Requirements
Removed psycopg2 from requirements.txt as other database types are supported ([Pull request](https://github.com/carrotquest/django-clickhouse/pull/16) by Devkalion)

Bug fixes
Fixed infi.clickhouse-orm compatibility issue (bug in migration fields imports)

Initial release