* TIM-39 partial: peer evaluators being shown other students' submissions and
  a rubric, and feedback in the form of radio buttions is being solicited.
  This is *mostly* plumbed through to the API.
* TIM-53 complete
* TODO: Needs tests, needs rubric_criteria refactoring

Co-authored-by: Joe Blaylock <jrbl@jrbl.org>

Jrbl/xblock submit return type

* Removed commented-out nascent Rubric model implementation

* Basic parsing of XML rubric's in @ormsbee's proposed format
* Rubrics displayed to user after they've made at least one submission
* Multiple rubrics on the workbench with different evaluation criteria

Creating a debug page for evaluations.

* Updates to API error checking and reporting to make it possible to
  report error conditions back to the user (though in production we'll
  generally not want to burden them with this information.)
* CSS and javascript fixes to reflect same.
* Beginning of HTML escaping of prompts introduced, but that part is
  incomplete as yet.

WIP: Outlining the API intended for Peer Grading Workflow.

Added some additional documentation. Some quick cleanup.

Almost entirely documentation.

Add XBlock and xblock-sdk dependencies separately

More mature error handling around API calls

* Catches SubmissionErrors and sends pass/fail information back to user
  via javascript hidden div.
* Renamed everything from _compose* to just _*
* CSS and js cleanups to make ongoing work less painful (I hope)

Fix sure lib at 1.2.3 because new version is broken.

Docs outline

Fixed conf.py file to work locally with RTD template and on RTD.

Update to XBlock version that installs workbench packages.

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