docs: document how to set heartbeat interval and election timeout
docs: document how to set heartbeat interval and election timeout

It gives more details about how to set heartbeat interval and election
timeout correctly based on RTT.

sebrandon1/etcd,visheshnp/etcd,honeyqa/etcd,akauppi/etcd,lumjjb/etcd,tguangch/etcd,SivagnanamCiena/etcd,gityf/etcd,yudai/etcd,Yhgenomics/etcd,wantonsolutions/dinv-etcd,linuxcer/etcd,mkumatag/etcd,heyitsanthony/etcd,delkyd/etcd,rnaveiras/etcd,onlyjob/etcd,jchauncey/etcd,svdata/etcd,a-robinson/etcd,qqsun8819/etcd,lumjjb/etcd,siddontang/etcd,HideoYamauchi/etcd,xiang90/etcd,mkumatag/etcd,mike-lerch/etcd,lorneli/etcd,HideoYamauchi/etcd,jlamillan/etcd,lorneli/etcd,zaphod-concur/etcd,wowsoso/etcd,li-ang/etcd,insequent/etcd,jefby/etcd,sayden/etcd,mickep76/etcd,vimalk78/etcd,coreos/etcd,achanda/etcd,heyitsanthony/etcd,westhood/etcd,glevand/coreos--etcd,snailwalker/etcd,lzbgt/etcd,snailwalker/etcd,combk8s/etcd,arthurcolle/etcd,raoofm/etcd,wantonsolutions/dinv-etcd,ravigadde/etcd,gyuho/etcd,spacejam/etcd,etcd-io/etcd,Yhgenomics/etcd,mqliang/etcd,cchamplin/etcd,jeremyeder/etcd,fanminshi/etcd,fgbreel/etcd,jonboulle/etcd,purpleidea/etcd,gouyang/etcd,YuleiXiao/etcd,freeloop1114/etcd,xychu/etcd,gae123/etcd,jlamillan/etcd,ktateish/etcd,xdlinear/etcd,rnaveiras/etcd,imzhulei/etcd,StorReduce/etcd,armstrongli/etcd,dnaeon/etcd,oscarrr110/etcd,rnaveiras/etcd,handsomesun/etcd,tamird/etcd,a-robinson/etcd,siddontang/etcd,hongbinz/etcd,etcd-io/etcd,nekto0n/etcd,mickep76/etcd,endocode/etcd,fgbreel/etcd,kkaneda/etcd,freeloop1114/etcd,luxas/etcd,glycerine/etcd,xiang90/etcd,joshix/etcd,Timer/etcd,bdarnell/etcd,spacejam/etcd,pauldallen/etcd,plasticbox/etcd,lzbgt/etcd,visheshnp/etcd,cockroachdb/etcd,cchamplin/etcd,xychu/etcd,etcd-io/etcd,glevand/coreos--etcd,plasticbox/etcd,glycerine/etcd,cockroachdb/etcd,armstrongli/etcd,tempbottle/etcd,bluebreezecf/etcd,jonboulle/etcd,sayden/etcd,Timer/etcd,iamqizhao/etcd,improbable-io/etcd,asim/etcd,betawaffle/etcd,onlyjob/etcd,jefby/etcd,hroyrh/etcd,yichengq/etcd,Winslett/etcd,Winslett/etcd,asim/etcd,li-ang/etcd,imzhulei/etcd,giantswarm/etcd,fanminshi/etcd,ravigadde/etcd,yudai/etcd,Eagle-X/etcd,linuxcer/etcd,shawnps/etcd,dnaeon/etcd,whuwxl/etcd,hongchaodeng/etcd,kkaneda/etcd,chipironcin/etcd,purpleidea/etcd,chenbaihu/etcd,mike-lerch/etcd,njucslqq/etcd,rchicoli/etcd,qqsun8819/etcd,tempbottle/etcd,bluebreezecf/etcd,swingbach/etcd,oscarrr110/etcd,fasaxc/etcd,pauldallen/etcd,buaazp/etcd,tguangch/etcd,wantonsolutions/dinv-etcd,sinsharat/etcd,endocode/etcd,luxas/etcd,dannysauer/etcd,rchicoli/etcd,beni55/etcd,StorReduce/etcd,TheHippo/etcd,gouyang/etcd,westhood/etcd,joshix/etcd,CrazyJvm/etcd,coreos/etcd,Eagle-X/etcd,yyljlyy/etcd,hroyrh/etcd,improbable-io/etcd,arthurcolle/etcd,hongbinz/etcd,raoofm/etcd,honeyqa/etcd,mkumatag/etcd,ajityagaty/etcd,mqliang/etcd,yyljlyy/etcd,gae123/etcd,SivagnanamCiena/etcd,delkyd/etcd,gyuho/etcd,bdarnell/etcd,combk8s/etcd,tamird/etcd,achanda/etcd,ktateish/etcd,whuwxl/etcd,TheHippo/etcd,chipironcin/etcd,OyTao/etcd_learning,njucslqq/etcd,betawaffle/etcd,OyTao/etcd_learning,msanterre/etcd,yichengq/etcd,shawnps/etcd,sebrandon1/etcd,CrazyJvm/etcd,chenbaihu/etcd,iamqizhao/etcd,xdlinear/etcd,sinsharat/etcd,akauppi/etcd,svdata/etcd,cognusion/etcd,buaazp/etcd,gityf/etcd,cognusion/etcd,giantswarm/etcd,sofuture/etcd,insequent/etcd,ajityagaty/etcd,nekto0n/etcd,swingbach/etcd,msanterre/etcd,handsomesun/etcd,zaphod-concur/etcd,vimalk78/etcd,shakefu/etcd,wowsoso/etcd,hongchaodeng/etcd,ajityagaty/etcd,fasaxc/etcd,beni55/etcd,YuleiXiao/etcd,shakefu/etcd,fasaxc/etcd,jeremyeder/etcd,sofuture/etcd,mqliang/etcd,dannysauer/etcd,jchauncey/etcd