:handshake: Add django-classy-settings (#243)

* Add django-classy-settings

* :pencil: Update README.md

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Co-authored-by: Jeff Triplett <jefftriplett@users.noreply.github.com>

README.md

@@ -145,6 +145,7 @@ _For a complete listing of all available packages, see [Django Packages](https:/
 - [django-extra-settings](https://github.com/fabiocaccamo/django-extra-settings) - Config and manage typed extra settings using just the django admin.
 - [environs](https://github.com/sloria/environs) - Simplified environment variable parsing that comes with a [Django helper](https://github.com/sloria/environs#usage-with-django) that installs additional packages.
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+- [django-classy-settings](https://github.com/funkybob/django-classy-settings) - Class based settings to keep your environments in order, with easy access to typed environment variables.
 
 ### Content Management Systems
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