Added School, Position, and Tag models

Added School, Position, and Tag models to the about app.  Also
generated south migrations.
regenerated css on new machine
Added 'hide' field to About models, added migration
Added About model admin classes
Updated Main view

Updated main view to pass Positions and Schools to template, pre-
sorted by end date
Updated Positions template

Updated Positions template to dynamically list Positions from db
for authenticated users; updated Positions styles.