Translocation graph

Working example: http://bl.ocks.org/rkophs/d6292eb6453981dc3821

This is somewhat similar to the existing D3 Chord layout (http://bl.ocks.org/mbostock/4062006). However this allows one to show relationships or translocations between specific areas of a group/entity. This is especially useful in trans-location graphs used by many research areas in genetics. Examples at http://circos.ca/intro/published_images/.

I tried to implement this layout similarly to the existing Chord layout for simplicity.

However I also understand if this is better seen fit as a plugin rather than baked into the D3 source. I'm up for suggestions.