test(filter): use rsvp.Promise to make v0.10.38 tests pass
test(filter): use rsvp.Promise to make v0.10.38 tests pass

caitp/cauliflower-filter,stefanpenner/broccoli-persistent-filter,chadhietala/cauliflower-filter,chadhietala/broccoli-persistent-filter,jcope2013/broccoli-persistent-filter,stefanpenner/cauliflower-filter,joliss/cauliflower-filter,csantero/broccoli-persistent-filter,rwjblue/broccoli-persistent-filter,broccolijs/broccoli-filter,joliss/broccoli-filter,matthewjh/cauliflower-filter