Django Parallelization

[CleanCut]

We need to either:

• (enhancement) integrate with Django in a way that supports parallel testing
• (bug fix) detect Django usage and override processes down to 1.

The current behavior of requiring the user to just know that they need to configure Green to use 1 process under Django is a pain point for Django+Green users. Let's make it better!

See also #177 which prompted this issue.