doc: add a Custom etcd discovery service section
doc: add a Custom etcd discovery service section

Eagle-X/etcd,mickep76/etcd,qqsun8819/etcd,vimalk78/etcd,lumjjb/etcd,xdlinear/etcd,lorneli/etcd,msanterre/etcd,hpcloud/etcd,Winslett/etcd,tamird/etcd,axingblog/etcd,csuideal/etcd,purpleidea/etcd,tempbottle/etcd,arthurcolle/etcd,cockroachdb/etcd,tguangch/etcd,sebschrader/etcd,TheHippo/etcd,hzy001/etcd,yichengq/etcd,tamird/etcd,justintung/etcd,insionng/etcd,westhood/etcd,OyTao/etcd_learning,endocode/etcd,nieanan/etcd,chai2010-playground/etcd,dterei/etcd,wfxiang08/etcd,tguangch/etcd,jonboulle/etcd,beni55/etcd,junxu/etcd,steveeJ/etcd,Timer/etcd,sayden/etcd,princeqjzh/etcd,bdarnell/etcd,gityf/etcd,Timer/etcd,tangkun75/etcd,cchamplin/etcd,wantonsolutions/dinv-etcd,plasticbox/etcd,bakins/etcd,mitake/etcd,mqliang/etcd,etcd-io/etcd,whuwxl/etcd,TheHippo/etcd,mgoelzer/etcd-fork2,coreos/etcd,Eagle-X/etcd,ajityagaty/etcd,a-robinson/etcd,etcd-io/etcd,raoofm/etcd,msanterre/etcd,njucslqq/etcd,jmptrader/etcd,njucslqq/etcd,gtank/etcd,chipironcin/etcd,arthurcolle/etcd,a-robinson/etcd,imzhulei/etcd,glycerine/etcd,elimisteve/etcd,delkyd/etcd,mgoelzer/etcd-fork2,mitake/etcd,glycerine/etcd,swingbach/etcd,wowsoso/etcd,dterei/etcd,mwitkow-io/etcd,csuideal/etcd,beni55/etcd,yichengq/etcd,bdarnell/etcd,chipironcin/etcd,rnaveiras/etcd,jeremyeder/etcd,polvi/etcd,cognusion/etcd,cchamplin/etcd,zaphod-concur/etcd,zaphod-concur/etcd,StorReduce/etcd,mkumatag/etcd,chai2010-playground/etcd,wfxiang08/etcd,SivagnanamCiena/etcd,devfreesg/etcd,pengzj/etcd,wowsoso/etcd,gosharplite/etcd,HideoYamauchi/etcd,gityf/etcd,pauldallen/etcd,robszumski/etcd,whuwxl/etcd,swingbach/etcd,spacejam/etcd,giantswarm/etcd,dannysauer/etcd,chai2010/etcd,shawnps/etcd,jchauncey/etcd,rchicoli/etcd,heyitsanthony/etcd,qiaochao911/etcd,fanminshi/etcd,glensc/etcd,youxidev/etcd,shafreeck/etcd,xueshanf/etcd,chai2010/etcd,heyitsanthony/etcd,mwitkow/etcd,jefby/etcd,ajityagaty/etcd,handsomesun/etcd,improbable-io/etcd,youxidev/etcd,jeremyeder/etcd,kingland/etcd,jlamillan/etcd,njharman/etcd,shakefu/etcd,SivagnanamCiena/etcd,honeyqa/etcd,betawaffle/etcd,ecnahc515/etcd,mike-lerch/etcd,delkyd/etcd,YuleiXiao/etcd,hongchaodeng/etcd,wantonsolutions/dinv-etcd,armstrongli/etcd,olark/etcd,mqliang/etcd,hongbinz/etcd,joshix/etcd,oscarrr110/etcd,sofuture/etcd,ktateish/etcd,akauppi/etcd,armstrongli/etcd,dnaeon/etcd,fasaxc/etcd,chenbaihu/etcd,onlyjob/etcd,offscale/etcd,princeqjzh/etcd,qqsun8819/etcd,sinsharat/etcd,mwitkow-io/etcd,gouyang/etcd,sinsharat/etcd,xebitstudios/etcd,yudai/etcd,lorneli/etcd,plasticbox/etcd,jravetch/etcd,mickep76/etcd,junxu/etcd,betawaffle/etcd,bluebreezecf/etcd,joshix/etcd,olark/etcd,xychu/etcd,Winslett/etcd,ecnahc515/etcd,bspline/etcd,ajityagaty/etcd,nkhare/etcd,kingland/etcd,qiaochao911/etcd,HideoYamauchi/etcd,dnaeon/etcd,fgbreel/etcd,StorReduce/etcd,oscarrr110/etcd,akauppi/etcd,nkhare/etcd,coreos/etcd,devfreesg/etcd,rchicoli/etcd,fanminshi/etcd,achanda/etcd,robszumski/etcd,yifan-gu/etcd,openedbox/etcd,es-chow/etcd,westhood/etcd,elimisteve/etcd,dannysauer/etcd,xiang90/etcd,sayden/etcd,buaazp/etcd,hroyrh/etcd,ylong/etcd,tempbottle/etcd,imzhulei/etcd,gtank/etcd,tangkun75/etcd,asim/etcd,asim/etcd,pengzj/etcd,hroyrh/etcd,visheshnp/etcd,gyuho/etcd,sofuture/etcd,xychu/etcd,sebrandon1/etcd,justintung/etcd,visheshnp/etcd,glevand/coreos--etcd,jmptrader/etcd,giantswarm/etcd,insequent/etcd,hongbinz/etcd,gae123/etcd,achanda/etcd,raoofm/etcd,shafreeck/etcd,nieanan/etcd,svdata/etcd,ktateish/etcd,yifan-gu/etcd,li-ang/etcd,barakmich/etcd,yyljlyy/etcd,bspline/etcd,CrazyJvm/etcd,sebrandon1/etcd,mike-lerch/etcd,svdata/etcd,hpcloud/etcd,lumjjb/etcd,linuxcer/etcd,jchauncey/etcd,cockroachdb/etcd,barakmich/etcd,gyuho/etcd,mischief/etcd,gae123/etcd,shawnps/etcd,kkaneda/etcd,YuleiXiao/etcd,cognusion/etcd,vimalk78/etcd,es-chow/etcd,jonboulle/etcd,rnaveiras/etcd,yudai/etcd,mkumatag/etcd,fgbreel/etcd,yyljlyy/etcd,spacejam/etcd,glevand/coreos--etcd,CrazyJvm/etcd,gosharplite/etcd,shakefu/etcd,lzbgt/etcd,honeyqa/etcd,ylong/etcd,handsomesun/etcd,nekto0n/etcd,gouyang/etcd,etcd-io/etcd,freeloop1114/etcd,siddontang/etcd,bakins/etcd,luxas/etcd,endocode/etcd,purpleidea/etcd,ravigadde/etcd,polvi/etcd,nekto0n/etcd,iamqizhao/etcd,chenbaihu/etcd,mqliang/etcd,jlamillan/etcd,jefby/etcd,bluebreezecf/etcd,ravigadde/etcd,combk8s/etcd,xiang90/etcd,rnaveiras/etcd,onlyjob/etcd,sebschrader/etcd,snailwalker/etcd,hongchaodeng/etcd,steveeJ/etcd,insionng/etcd,Yhgenomics/etcd,crandles/etcd,combk8s/etcd,QuantiumTechnology/etcd,improbable-io/etcd,QuantiumTechnology/etcd,buaazp/etcd,mwitkow/etcd,Yhgenomics/etcd,dalanlan/etcd,kkaneda/etcd,insequent/etcd,linuxcer/etcd,iamqizhao/etcd,xdlinear/etcd,xebitstudios/etcd,snailwalker/etcd,OyTao/etcd_learning,luxas/etcd,crandles/etcd,hzy001/etcd,mkumatag/etcd,lzbgt/etcd,siddontang/etcd,jravetch/etcd,glensc/etcd,offscale/etcd,dalanlan/etcd,fasaxc/etcd,xueshanf/etcd,openedbox/etcd,wantonsolutions/dinv-etcd,pauldallen/etcd,axingblog/etcd,freeloop1114/etcd,fasaxc/etcd,njharman/etcd,li-ang/etcd,mischief/etcd