Partitioner: add throttled queue to ReducerClient
Partitioner: add throttled queue to ReducerClient

Also:
 - emit an event when a chunk is reduced

This is breaking the style everywhere else in the
app where socket decoration is left to the App file
to maximise discovery. This way is growing on me
as the nicer option though - will probably refactor
elsewhere later.	
andrewpmckenzie/node-map-reduce,andrewpmckenzie/node-map-reduce,andrewpmckenzie/node-map-reduce