v3.0.0

• Add topojson.filterAttachedWeight.
• Change topojson.presimplify to return a shallow copy rather than modifying the topology.
• Change topojson.presimplify to remove quantization, if any, on the output topology.
• Change topojson.simplify to return a shallow copy rather than modifying the topology.
• Change topojson.filter to return a shallow copy rather than modifying the topology.
• Fix topojson.planarTriangleArea, which was returning twice the intended area.
• Fix topojson.sphericalTriangleArea to be consistent with d3.geoArea.
• Fix topojson.sphericalRingArea to be consistent with d3.geoArea.