Fix problems due to Django version change

This change fixes a set of issues related to Django upgrade.

* Updated manage.py
* Removed mail/ folder that was created because we were using a very outdated version of Python
* Fixed import paths in a couple of places due to the new convention.
* Fixed the old pickle file related to toy example.

Other than sbml and mail sending, all other tests should pass. We need to fix the test fixture as well, but it is a minor issue. 

This should be ready to be deployed into EC2 when DB is properly configured.