refactor lookupd utils for re-usability:

* and as a result refactor nsqadmin graph handling
nsqadmin: ensure that rates are never negative
nsqadmin: fix counter template error
nsq_stat: "iostat" like utility for aggregate NSQ cluster stats
Merge pull request #173 from mreiferson/nsq_stat_173

command line utility (nsq_stat)
record deferred count as a gauge not a rate
Merge pull request #179 from jehiah/deferred_count_as_gauge_179

record deferred_count as a guage instead of a counter in graphite
fix installation of nsq_stat
Merge pull request #180 from ploxiln/install_nsq_stat_180

nsq_stat installed wrong
nsq_to_http: add --mode option (with *new* hostpool mode)

* deprecate --round-robin and plan on deprecating the all aka multicast mode
Merge pull request #174 from mreiferson/nsq_to_http_hostpool_174

nsq_to_http: add host pooling option for handling upstreams
update ChangeLog
init add writer

allow custom heartbeat interval setting when call NewWriter()
auto send IDENTIFY when call ConnectToNSQ()
write message via Publish()/MultiPublish()