Django-address

Corrected a metadata issue during publishing.

Django Address now uses AutoField for default IDs.

Principle changes:

* Improved admin search capabilities.
* Admin bug fix.

Additional changes:

* Minor updates to the structure of the example site.
* Dockerisation of the example site.
* Addition of tox testing.
* Normalisation of the code using Black.

This release improved project administration and resolved some bugs.

Summary of project updates:

* 123 - Added documentation on how to run project tests
* 125 - Added Github Action-based automated testing (see [recent results](https://github.com/furious-luke/django-address/actions))
* 125 - Investigated and removed outdated test 
* 50 - Update State model to allow for Mexican state codes longer than two characters

Additional results from this release:

* 82 - Made a lot of progress investigating US territories and determined a path forward for this ticket
* 128, 129 - Created these project administration tickets as to-dos
* 127 - Added this ticket as part of a focus on checking that this package follows best practices for stand-alone packages

This release of `django-address` closes a variety of minor bugs and improves functionality.

Summary of project updates:
- Updated use of tags in project administration
- Added support for additional UK addresses
- Enhanced `AddressField` on_delete policy to handle `null=True`
- Visual improvement to Django Admin field
- Light enhancements to example app
- Added Sponsor project button meta :)

For a details of complete Issues, please consult the [release milestone](https://github.com/furious-luke/django-address/milestone/3?closed=1).