My first pass at populating the submission API.

Conflicts:
	requirements/test.txt

Docs outline

1. Picks up Django settings.
2. Includes the root README.rst file into the docs.
3. Points to the new locations for our apps.

More documentation, repr, corner case testing, and proper validation

Updating the settings files to pick up the new applications

WIP: First pass at creating BDD tests for the Problem Creation stories

These tests are a first attempt at defining the story. The underlying methods are all empty, and will be filled out with the implementation.  I believe some steps may overlap and need to be refactored, and perhaps some of the stories belong in common_grading instead of peer_grading. I want Will to review this and see if I'm going down the correct path before I fill out any more of these for the first sprint.

WIP: Rough sketch at responsibility split between submissions/scores storage and workflow

Update setup.py to handle -e in requirements.txt

Added setup.py to make packages installable

Use pure XBlock instead XModule.

Remove django-rest-framework

Adjust types and limits for common_grading/models.py