Travis: separate dependency installation from Lwt
Travis: separate dependency installation from Lwt

c-cube/lwt,rgrinberg/lwt,ocsigen/lwt,rgrinberg/lwt,rneswold/lwt,rgrinberg/lwt,rneswold/lwt,rgrinberg/lwt,ocsigen/lwt,c-cube/lwt,c-cube/lwt,ocsigen/lwt,rneswold/lwt