README: require Go 1.10+
README: require Go 1.10+

Signed-off-by: Gyuho Lee <3454051ee3341eb69bdf6fca40899cdad4d86496@gmail.com>

sebrandon1/etcd,fanminshi/etcd,xiang90/etcd,glevand/coreos--etcd,joshix/etcd,vimalk78/etcd,gyuho/etcd,sebrandon1/etcd,lorneli/etcd,sinsharat/etcd,vimalk78/etcd,ajityagaty/etcd,rnaveiras/etcd,li-ang/etcd,etcd-io/etcd,cockroachdb/etcd,bdarnell/etcd,cockroachdb/etcd,rnaveiras/etcd,gyuho/etcd,rnaveiras/etcd,dannysauer/etcd,ajityagaty/etcd,joshix/etcd,mkumatag/etcd,ajityagaty/etcd,lorneli/etcd,fanminshi/etcd,etcd-io/etcd,xiang90/etcd,sinsharat/etcd,glevand/coreos--etcd,mkumatag/etcd,mqliang/etcd,mqliang/etcd,li-ang/etcd,coreos/etcd,mqliang/etcd,dannysauer/etcd,etcd-io/etcd,bdarnell/etcd,coreos/etcd,mkumatag/etcd