Update carto bin to use millstone if available.
Update carto bin to use millstone if available.

madeinqc/carto,CartoDB/carto,pnorman/carto,tomhughes/carto,whitelynx/carto,CartoDB/carto,mapbox/carto,stefanklug/carto,1ec5/carto,gravitystorm/carto,clhenrick/carto,midnightcomm/carto