• 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.