This way, we don't need symlinks (which don't work on Windows). This commit also
simplifies the structure of the flare.json file, so that we don't need to tricky
conversion of the JSON map—it can be read directly by the hierarchy layout.
This method can be used for computing the bounding box of arbitrary GeoJSON
objects. This commit also fixes a bug in d3.geo.path, such that it will accept
any GeoJSON object, rather than requiring GeoJSON feature objects.
Mike Bostock