Allow null geometry objects. Fixes #18.
Use spherical area for simplification.
Oops, fix conversion between absolute & relative.
Use absolute area for simplification.
Port d3.geo.area to compute triangle area.
Fix for counterclockwise triangles.
Fix (again) for spherical triangle area.
Document units for simplification.
Slight optimisation.
Merge branch 'simplify-spherical-area' of https://github.com/jasondavies/topojson into simplify-spherical-area
Merge branch 'simplify-spherical-area'
Update version number.