Rename redis "roomparticipant" to "roomparticipants".
Rename redis "roomparticipant" to "roomparticipants".

In addition to being cleaner, this will help have two different namespaces for
the participants lists (one for 0.13.2 and one for after).

magopian/loop-server,magopian/loop-server,kitcambridge/loop-server,kitcambridge/loop-server,mozilla-services/loop-server,mozilla-services/loop-server