- Change topojson.bbox to return a new bounding box rather than modifying the topology.
- Change topojson.quantize to return a shallow copy rather than modifying the topology.
- Allow topojson.quantize to take an optional transform object.
- Change topojson.transform to return a new point, rather than modifying it.
- Change topojson.untransform to return a new point, rather than modifying it.