Merge pull request #4 from dulaccc/improve-settings

Add a setting to disable the bulk create
Merge pull request #3 from dulaccc/custom-user-models

Support custom user models
Freeze the user email address

useful if the user change the email associated to his account, then
we've kept the email used for this particular notification
Update the manage.py code to a more recent version
Add south to the test application (to easily generate schema migrations)
Wrap the user object into a AlertUser class

so we can user User instances or even just email address strings
Merge branch 'recipients-specified-by-email-only' into develop