updated django-mailer-2

I have made some minor improvements to django-mailer2:

* added cleanup_mail from a patch from https://github.com/SmileyChris/django-mailer-2/pull/16

* refactored the test so you don't need to have a Django project to test it

* added a demo project to show how we can retrieve mail info

* published doc in readthedocs

* minor bug on unicode mail

* improved admin list