Add docs for creating model and model tests
Improve instructions for adding posts to admin
Add instructions for starting TDD process
Screenshots and round out model testing a bit
Merge remote-tracking branch 'origin/master' into models

Conflicts:
	tutorials/index.rst
Updated the models section with minor changes

- added some tips and hints
- removed a couple unnecessary things like full tracebacks
Added some more explanations to models
Merge branch 'models'
Merge branch 'master' of github.com:pythonsd/learning-django-by-testing

Conflicts:
	tutorials/index.rst