New formula: tippecanoe, a tool for map data processing

This adds a new formula for Eric Fischer's tippecanoe project.
The project depends on protocol buffers and sqlite, takes
GeoJSON as input and produces MBTiles as output.
It's the initial release (though the project is already in heavy usage), and I usually go with v0.0.0. Some people choose v1.0.0. Happy to go v1.0.0 if that connotes value.