client: clean up README
client: clean up README

Address rob's comments about sentences in README.

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