When a new model is added, it should be rendered respecting the collection's comparator

So I followed your recommendation for contributing.

Here's a specific branch for the following spec 

  - given the collection is not empty
  - given the collection as a comparator
  - when a model is added to the collection
  - the new model should be added to the dom in the right order, respecting the collection's comparator

The test is currently failing.