Update deprecated togeojson dependency

[NatanKanitz]

npm WARN deprecated [email protected]: This module has moved: please install @mapbox/togeojson instead

[pkeller3]

Tom, the original author, wrote "This is a maintained and modernized fork of the toGeoJSON project, which I (Tom) wrote while at Mapbox, and am now maintaining on a personal basis because the Mapbox-owned project is abandoned." I think the dependency should be changed to his version of the library.

[leplatrem]

Cool! thanks! You should update the package.json file too I guess ;)