1) '_project' is a django project file in Ulipad. Ulipad is a python IDE, recommended!
2) remove 'info' app, added 'purchase' app, from now on, all app are based on the role in real world, so that makes it easier to use django's defualt auth system
3) added simple html page for login, ugly though. Need CSS decoration.
4) refactored models, to maximize code reuse.