not expecting nitro to be present on travis, so pin BUILD_PLUGIN_NITRO=OFF
not expecting nitro to be present on travis, so pin BUILD_PLUGIN_NITRO=OFF

DougFirErickson/PDAL,boundlessgeo/PDAL,jwomeara/PDAL,mtCarto/PDAL,Sciumo/PDAL,mpgerlek/PDAL-old,lucadelu/PDAL,jwomeara/PDAL,Sciumo/PDAL,radiantbluetechnologies/PDAL,lucadelu/PDAL,radiantbluetechnologies/PDAL,Sciumo/PDAL,jwomeara/PDAL,mpgerlek/PDAL-old,boundlessgeo/PDAL,lucadelu/PDAL,mtCarto/PDAL,mpgerlek/PDAL-old,jwomeara/PDAL,DougFirErickson/PDAL,mtCarto/PDAL,Sciumo/PDAL,boundlessgeo/PDAL,DougFirErickson/PDAL,lucadelu/PDAL,radiantbluetechnologies/PDAL,radiantbluetechnologies/PDAL,mtCarto/PDAL,boundlessgeo/PDAL,DougFirErickson/PDAL,mpgerlek/PDAL-old