Django-herald

- Added support for automatic HTML2text support for plain text emails
- Added auto-complete for user in admin
- 74 - Added support for conditional enable/disable to raise error for missing templates `HERALD_RAISE_MISSING_TEMPLATES`
- Updated to use GitHub Actions for CI
- Switched to Black for code formatting

- Fix bug that could occur sometimes in herald.contrib.auth when reversing the password reset url
- Add feature to automatically delete old notifications after configured period of time
- Don't set base_url to empty string when DEBUG==True
- Fix for attaching files to a notification that may be closed before the notification is sent
- Text view for viewing notification now uses the text/plain content type, and the default charset setting

- Drop official support for django < 1.11 and python 3.2-3.3
- Changed Notification.notification_class and Notification.verbose_name fields to have less restrictive `max_length`
- Added support for django 2.1
- Added support for python 3.7

- Changed SentNotification.error_message to a TextField to fix issues when message is longer than 255 characters

- Fix for migration bug introduced in 0.1.7

- User disabled notifications support