Remove NamedModel and NamedCreatedModel abstract models

This inheritance relationship caused more trouble than it was
worth. They saved a few lines of code, but now we are finding
that we want to change the core attributes on the inheriting.
Use requirements.txt in build and fix Django at 1.4
Merge pull request #108 from steventlamb/remove_inherited_models

Remove NamedModel and NamedCreatedModel abstract models