Added docs for ratio and percent gauges.
Added docs for ratio and percent gauges.

dropwizard/metrics,ind9/metrics,jplock/metrics,cirrus-dev/metrics,signalfx/metrics,unitsofmeasurement/metrics,valery1707/dropwizard-metrics,mveitas/metrics,chenxianghua2014/metrics,rexren/metrics,fcrepo4-archive/metrics,mattnelson/metrics,thelastpickle/metrics,gorzell/metrics,bentatham/metrics,gburton1/metrics,randomstatistic/metrics,kevintvh/metrics,mveitas/metrics,mt0803/metrics,jasw/metrics,maciej/metrics-scala,wfxiang08/metrics,infusionsoft/yammer-metrics,timezra/metrics,mspiegel/metrics,gburton1/metrics,ChetnaChaudhari/metrics,slovdahl/metrics,mnuessler/metrics,Banno/metrics,gorzell/metrics,egymgmbh/metrics,scullxbones/metrics-scala,infusionsoft/yammer-metrics,tempredirect/metrics,mtakaki/metrics,dropwizard/metrics,erikvanoosten/metrics-scala,gorzell/metrics,dropwizard/metrics,fcrepo4-archive/metrics,AltitudeDigital/metrics,wickedshimmy/metrics-scala,slachiewicz/metrics,ohr/metrics