Shopify/batman — pull request #607 by mattwdh (2012-12-05 01:12:26+00:00)
Title: Faster sort

*Part One*
+ During the development of Shopify 2 we wondered if adding many new values to the set only reindexed the set once. I've added a test to confirm this.
+ In order to mock `_reIndex` properly I needed to change how it was bound.

*Part Two*
+ I've added `_mapIdentities` to `Batman.Model` such that when we add multiple items to a set we do it all at once. The `_mapIdentity` API is staying the same so this is a non-breaking change. We played around with various implementations, and this was a good mix of clean yet efficient.

/cc @hornairs @nciagra @kristianpd