When an item is being removed because of its destroy signal, we were removing

an extra item as well. What was happening is that the item's view would notice

that its underlying model was destroyed, and it would remove itself. The list

view would then see the removal from the collection, and remove whatever

element was at that same index.
I've changed it so that instead of blindly selecting an element by index, we

instead keep an array of the child views and look up which one needs to be

removed by its model.

Ran js-tests that used this (and were failing before).