Related name to EvaluationCriterion.assignment
Merge branch 'feature-peerreview' of github.com:OpenMOOC/moocng into feature-peerreview

Conflicts:
	moocng/peerreview/models.py
Fixed typos with criterion/criteria.
Singular: criterion
Plural: criteria
Wrong: criterias (fixed)
Send mail when a peer assignment review is done
Merge branch 'feature-peerreview' of github.com:OpenMOOC/moocng into feature-peerreview