Updated travis to use virtualised linux env
Updated travis to use virtualised linux env

tomalrussell/smif,nismod/smif,willu47/smif,willu47/smif,willu47/smif,nismod/smif,nismod/smif,willu47/smif,tomalrussell/smif,nismod/smif,tomalrussell/smif,tomalrussell/smif