add support for all statsd metric types

hey Shawn.  

following up on conversations about graphite and spread data post-LISA I thought I'd better go back through and implement support for statsd timers, counters and sets (initially we only supported emitting gauge-types).  This will allow a graphios user to add: 

_metrictype            timer

to a host or service definition and the statsd back-end will treat the metric as a timer (thereby allowing statsd to generate percentiles, min/max/count/sum etc.. for it). 

Love ya man.