support [0-9_] in CSS attribute names
support [0-9_] in CSS attribute names

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