clientv3: add initial kv api for client
clientv3: add initial kv api for client

joshix/etcd,fanminshi/etcd,jlamillan/etcd,CrazyJvm/etcd,glycerine/etcd,mickep76/etcd,lumjjb/etcd,armstrongli/etcd,achanda/etcd,handsomesun/etcd,bluebreezecf/etcd,swingbach/etcd,coreos/etcd,bdarnell/etcd,insequent/etcd,coreos/etcd,li-ang/etcd,sinsharat/etcd,vimalk78/etcd,etcd-io/etcd,purpleidea/etcd,li-ang/etcd,mkumatag/etcd,achanda/etcd,rnaveiras/etcd,linuxcer/etcd,akauppi/etcd,luxas/etcd,insequent/etcd,a-robinson/etcd,lorneli/etcd,sinsharat/etcd,yudai/etcd,sebrandon1/etcd,StorReduce/etcd,jlamillan/etcd,tamird/etcd,visheshnp/etcd,siddontang/etcd,tamird/etcd,cockroachdb/etcd,bdarnell/etcd,mkumatag/etcd,swingbach/etcd,CrazyJvm/etcd,mqliang/etcd,ravigadde/etcd,xiang90/etcd,rnaveiras/etcd,fanminshi/etcd,whuwxl/etcd,mickep76/etcd,nekto0n/etcd,dannysauer/etcd,zaphod-concur/etcd,xiang90/etcd,sofuture/etcd,plasticbox/etcd,westhood/etcd,endocode/etcd,shawnps/etcd,purpleidea/etcd,mkumatag/etcd,plasticbox/etcd,shawnps/etcd,westhood/etcd,etcd-io/etcd,a-robinson/etcd,handsomesun/etcd,ravigadde/etcd,vimalk78/etcd,luxas/etcd,jonboulle/etcd,armstrongli/etcd,OyTao/etcd_learning,raoofm/etcd,mqliang/etcd,hongchaodeng/etcd,nekto0n/etcd,lumjjb/etcd,ajityagaty/etcd,gyuho/etcd,joshix/etcd,ajityagaty/etcd,dnaeon/etcd,akauppi/etcd,tguangch/etcd,siddontang/etcd,linuxcer/etcd,rchicoli/etcd,heyitsanthony/etcd,visheshnp/etcd,glevand/coreos--etcd,dnaeon/etcd,whuwxl/etcd,tguangch/etcd,ajityagaty/etcd,dannysauer/etcd,wantonsolutions/dinv-etcd,jonboulle/etcd,sofuture/etcd,wantonsolutions/dinv-etcd,ktateish/etcd,hongchaodeng/etcd,ktateish/etcd,raoofm/etcd,rnaveiras/etcd,wantonsolutions/dinv-etcd,endocode/etcd,cockroachdb/etcd,YuleiXiao/etcd,StorReduce/etcd,zaphod-concur/etcd,gyuho/etcd,yudai/etcd,qqsun8819/etcd,glevand/coreos--etcd,OyTao/etcd_learning,bluebreezecf/etcd,chipironcin/etcd,glycerine/etcd,chipironcin/etcd,sebrandon1/etcd,lorneli/etcd,mqliang/etcd,rchicoli/etcd,YuleiXiao/etcd,heyitsanthony/etcd,etcd-io/etcd,qqsun8819/etcd