Addressing issue #346.

This should result in the following order of pending submissions on the
dashboard:

- those that have never received a nit (oldest first)

- those in which some previous iteration received a nit, but this one
  has not (oldest first)

- those in which there is at least one nit on the current iteration
  (newest first)
Merge pull request #352 from doncruse/master

Addressing issue #346.