ogr2ogr -f "GeoJSON" california_geojson.json tl_2010_06_zcta510.shp
topojson -o california_topojson.json california_geojson.json
ogr2ogr -f "GeoJSON" working/counties.geo.json assets/ca/counties.shp
ogr2ogr -f "GeoJSON" working/zipcodes.geo.json source/tl_2010_06_zcta510.shp
# merge two shapefils