error handling and trigger track on ops complete

exceptionCaught blocks for places outside of the protection
of promises.

TrackerHandler was listening to the queryPromise (ie. sourcePromise)
so it was likely logging completions too quickly
use channel readability triggers over backoff

need something for sendCompletes though
putting backoff back in for op-complete

should really just make a handler version of op processor for many
reasons and could just put the back-off logic there, but this has
been sitting for too long
fix writability logic