Do not use the submission_uuid from a response for peer
The Workflow API was still using the submission_uuid within a peer response.  Removed this, and updated tests accordingly.
Merge pull request #268 from edx/sanchez/fix_submission_uuid_use

Do not use the submission_uuid from a response for peer
Removing the peer uuid from the assessment api
Changing the Peer API signatures to use submission UUID instead of student items. This will greatly simplify our APIs uses and queries.