Add a model field for published/draft state

This involves adding two tutorials:
- Setting up South
- Adding this new model field and changing our code to use it

This will demonstrate:
- Setting up South
- Making a South migration to add a column
-  Changing our tests and code to iterate based on a new feature

I think this is a high priority feature.  Thoughts on this?  Ideas for implementation?  Who wants to take on this task?
