function d3_geo_bounds(o, f) {
  if (d3_geo_boundsTypes.hasOwnProperty(o.type)) d3_geo_boundsTypes[o.type](o, f);
}
Given a GeoJSON object, returns the corresponding bounding box. The bounding
box is represented by a two-dimensional array: [[left, bottom], [right,
top]], where left is the minimum longitude, bottom is the minimum latitude,
right is maximum longitude, and top is the maximum latitude.