Added djenv

Hello. For your consideration, I added djenv, which is a library that allows you to configure Django settings with environmental variables.  It automatically deciphers what environmental variables corresponds to what Django settings.  It also automatically casts the environmental variables into the right type.  Thank you for your time.

README.md

@@ -100,6 +100,7 @@ _For a complete listing of all available packages, see [Django Packages](https:/
 - [django-environ](https://github.com/joke2k/django-environ) - Environment variables.
 - [django-split-settings](https://github.com/sobolevn/django-split-settings) - Organize multiple settings files.
 - [django-constance](https://github.com/jazzband/django-constance) - A Django app for storing dynamic settings in pluggable backends (Redis and Django model backend built in) with an integration with the Django admin app.
+- [djenv](https://github.com/danieljdufour/djenv) - Load Django settings from environmental variables
 
 ### Content Management Systems
 - [wagtail](https://github.com/wagtail/wagtail) - Popular Django content management system (CMS). See [awesome-wagtail](https://github.com/springload/awesome-wagtail) too.