AppVeyor: pin gdal and fiona
AppVeyor: pin gdal and fiona

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