implement delayed call/branch deletion

Squashed commit of the following:

commit 5539a3dcb4657033f35867872d2af1833ca851de
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Wed Aug 27 08:02:00 2014 -0400

    update redis mod version

commit fa372760a2663b11352edf61de7ab0ba4d2c8fb7
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Tue Aug 26 15:42:00 2014 -0400

    delay branch deletion

commit 87af9f48f532d9a17aa69413b53a143665cb6d95
Author: Richard Fuchs <rfuchs@sipwise.com>
Date:   Tue Aug 26 13:52:28 2014 -0400

    delay deletion of entire call