testUpdateNonExistingProposal unit test added.
testUpdateNonExistingProposal unit test added.

It checks that 404 response code is returned when a student tries to update a proposal which does not exist. It currently fails, as the checkAccess function does not have a check if the requested GSoCProposal entity was retrieved.

rhyolight/nupic.son,rhyolight/nupic.son,rhyolight/nupic.son