Added pyyaml to travis config
Added pyyaml to travis config

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