tabindex is not respected

I've been trying to use the alpha-4 release of this component to replace `ember-list` in an Ember app I've been upgrading from Ember 1.11 (still). Unfortunately, I immediately ran into a problem with `tabindex`, which we were using to allow the user to navigate the list using focus. It seems that `ember-collection` is relying on `translate` to put items in the visually correct order, but `tabindex=0` relies on the actual order of the elements in the document. I don't know if I'm observing a bug, or if it was implemented that way for performance reasons, but in my case, preserving the correct tab order is important.