RiveraGroup/mungedb-aggregate — pull request #25 by jhallriverainc (2014-10-27 01:26:57+00:00)
Title: EAGLESIX-2708 expression Subtract ported to mongo 2.6.5

It looks like they're manually figuring out what do to for (number, number), (date, date), (date, number) so I implemented that and wrote new test cases for them.