Given a csv of geospatial points and a shapefile, create a clipped voronoi tessellation

[mikefab]

A clipped Voronoi diagram is one that is confined to a compact domain (i.e. a bounded and closed 2D region or a 3D volume). In the example above, a normally generated Voronoi diagram will have some cells infinite or partially outside of the country boundary. However, only the cells that lie within the country boundary are of our interests.

Admin 1 geojson: http://myjson.com/wvt2s

The output of this task could be used as input to #44.