ORA AI and Peer acceptance tests

Added stub XQueue server to bok_choy test suite.
Added feedback check for AI-assessment test
Added peer assessment feedback test

To run (in devstack): `rake test:bok_choy[test_ora.py]`

Notes:
* This PR tests *receiving* peer-grades, but not *giving* peer-grades; that will come in a later PR.
* This uses old-style `bok-choy` rather than the page-object based interface @cpennington is working on: https://github.com/edx/bok-choy/pull/18  If that gets merged before this PR, I will rebase and update the tests to use the new interface.
* @olmar This PR adds a script for running stub servers manually, which may be useful.

Reviewers: @jzoldak @stephensanchez