Merge pull request #250 from jehiah/lookupd_poll_interval_250

reader: distribute lookupd requests
update ChangeLog
nsqd: send mem/gc stats to statsd

* use int64 for statsd client values
* add --statsd-mem-stats flag, default on
Merge pull request #249 from mreiferson/mem_statsd_249

nsqd: mem and GC stats over statsd
RDY Improvements

* set RDY 0 immediately on backoff
* force RDY bootstrapping on new connection
* send truncated RDY value instead of none when over max-in-flight