GeoJSON squares

A really, really simple example about the usage of GeoJSON and D3's geo path generators with purely geometrical (non-geographical) data.

It creates a GeoJSON polygon representing a square for each pair of coordinates in the input data, then it packs all polygons in a feature collection. In order to use the path generator, a custom projection is defined, representing the identity (I don't know if there is a better way to implement that). A feature's type property is then used to color the rendering.