Easier removal on exit transition.

[mbostock]

Currently, it's a bit of a pain to remove elements after an exit transition:

selection.exit()
  .transition()
    …
    .each("end", function() { d3.select(this).remove(); });

I could see this being easier if either the this context was a singleton selection, in which case you could say:

.each("end", function() { this.remove(); })

Or, if there were a unified transition end event, in which case you might say:

.on("end", function() { this.remove(); })

where this refers to selection, rather than a singleton selection. I suppose if we had unified transition events, that trigger individually for staggered transitions (variable delay or duration) or collectively for non-staggered transitions (uniform delay and duration), then we could use the later on("end", …) in either case, which seems nice.

[mbostock]

Transition supports remove, now. So fixed.