Transitioned to PostGIS, updated models and initial_data fixture.

Set up database connections for postgres and created secret key to hide username and password. Added latitude, longitude and point fields to person and marker model.  Updated the initial_data fixture to include the added fields. Also update requirements text to include geospatial libraries.
Merge pull request #16 from jzmiller1/geodjango_fb

Transitioned to PostGIS, updated models and initial_data fixture.