Django-mjml

*  Added supporting Django v3.1

* Added `requests` in extras require in `setup.py`
* Added MJML 4.6.3 in tests
* Upgraded MJML to 4.6.3 in dockerfile
* Updated docs

* Added supporting Django v3.0
* Added supporting render http-server (including official MJML API https://mjml.io/api)
* Added Python 3.8 in tests
* Added MJML 4.5.1 in tests
* Upgraded MJML to 4.5.1 in dockerfile
* Upgraded Node to v12 for tcp-server
* Reorganized tests
* Updated docs

* Fixed a trouble with unicode
* Added MJML 4.4.0 in tests
* Upgraded MJML to 4.4.0 in dockerfile

* Removed MJML 4.0.5, 4.1.2 and 4.2.1 from tests
* Added MJML 4.3.1 in tests
* Updated tcp-server adding cleanly termination
* Upgraded MJML to 4.3.1 in dockerfile
* Updated dockerfile by using `exec`
* Added supporting Django v2.2

* Added `MJML_CHECK_CMD_ON_STARTUP` setting (thanks to Marcel Chastain)
* Added Python 3.7 in tests
* Added MJML v.4.2.1 in tests
* Removed MJML v.2.3.3 from tests
* Updated MJML to 4.2.1 in docker