bump to v5.0.3 with new filter keywords support
bump to v5.0.3 with new filter keywords support

gravitystorm/mapnik-reference,mapnik/mapnik-reference,mojodna/mapnik-reference,florianf/mapnik-reference,mojodna/mapnik-reference,mapnik/mapnik-reference,florianf/mapnik-reference,gravitystorm/mapnik-reference,mapnik/mapnik-reference,CartoDB/mapnik-reference,CartoDB/mapnik-reference,mapycz/mapnik-reference,mapycz/mapnik-reference