fix doc build instructions
fix doc build instructions

dreamhost/cliff-tablib,idjaw/cliff,enzochiau/cliff,dtroyer/cliff,idjaw/cliff,openstack/cliff,varunarya10/cliff,dtroyer/cliff,citrix-openstack-build/cliff,varunarya10/cliff,enzochiau/cliff,openstack/cliff,hguemar/cliff-tablib,dhellmann/cliff-tablib,citrix-openstack-build/cliff