fix(README): remove the drone.io badge
fix(README): remove the drone.io badge

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