Wiring up submissions

* Connects the Tim Composition XBlock to the Submissions API so that you
  can submit a composed response.

Running XBlock Workbench in edx-tim

Sanchez/debug submissions page

* Implement a basic XBlock for composing. Allows the user to enter text
  and see what they entered.
* Dirty shell script to install the XBlock demos into this working tree
  so that we can use the workbench for early prototyping. This should
  not be used any more once we integrate into LMS, obviously.

My first pass at populating the submission API.

Conflicts:
	doc/source/conf.py

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