Merge pull request #5 from djibon/master

This closes the issue.  Great Job!
making database drivers an optional part of the install
Fixing the Secret key in the template
Adding the heroku files
splitting vagrant specific provisioning out
Updating get_user_model for 1.7
Updating User Foreign Key for 1.7
Updating to the latest celery configuration
I should have merged earlier
merge
changes:

- added ShortCode table
- inserted IntroductionComment when reading an email based on references (message_id)