Adding changelog.
Adds a name to the `send_mail` task
Pass the model pk around, not the instance
Adds a method to save a MailerMessage without sending the e-mail
Adds functionality to attach files to MailerMessages
Remove `tests.py` file
Adds basic documentation for `add_attachment`
Cleanup tests
Cleanup documentation
Make compatible with Celery 2.5
Merge pull request #21 from Matt-Stevens/master

Support for file attachments
Make tests compatible with Django 1.3
Merge pull request #23 from Matt-Stevens/fix/test_compatibility

Make tests compatible with Django 1.3