KAZOO-1179: add callflow skel module
KAZOO-1179: add first crack at cf_sleep

Allows specifying timeouts in a handful of units for convenience
Constrains timeout to 24 hours on the high end.
KAZOO-1179: update header
KAZOO-1179: don't sleep past a hangup
KAZOO-1179: add a timeout-able wait_for_hangup/unbridge
KAZOO-1179: compare ecallmgr node to event's ecallmgr node
KAZOO-1179: use os:timestamp/0 in lieu of erlang:now/0
Merge pull request #220 from 2600hz/KAZOO-1179

Kazoo 1179