fix up vagrant configuration a bit to protect my machine-specific and osx-specific stuff
fix up vagrant configuration a bit to protect my machine-specific and osx-specific stuff

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