mbostock/d3 — pull request #716 by natevw (2012-07-21 01:02:35+00:00)
Title: Pass nested selection group index to event listeners

Not sure where in the documentation I discovered this (it's not typically mentioned) but in a nested selection, the "group" index is actually [passed to callbacks as the third argument](https://github.com/mbostock/d3/blob/master/src/core/selection-each.js#L10). This fixes the `selection.on` code so it doesn't drop arguments from `selection.each`.