TopoJson driver

[ebocher]

TopoJson encodes a collection of GeoJson into a topology scheme.
Specification here https://github.com/topojson/topojson saids

"TopoJSON is substantially more compact than GeoJSON, frequently offering a reduction of 80% or more even without simplification. Yet encoding topology also has numerous useful applications for maps and visualization above"

It makes sense to propose a driver to import and export topojson file.