title: underscore each method not running through the complete backbone collection
body: <p>I have a table that I am populating when new items are added to a collection and I am populated a deleted items collection when Items are deleted from that collection.</p>
  
  <p>Then I have a single save button, that triggers the save/delete events on the collections.</p>
  
  <p>Saves are working just fine but only half of my deletes are working and I am confused.</p>
  
  <pre><code>class MyApp.Collections.DeletedTasks extends Backbone.Collection
    model: MyApp.Models.Task
  
    destroy: () -&gt;
      console.log('destroy the collection size: ' + @.models.length)
      _.each(@.models, @sendDelete)
  
    sendDelete: (model) -&gt;
      console.log('deleting model with id: ' + model.get('id'))
      model.destroy()
  </code></pre>
  
  <p>Console output</p>
  
  <pre><code>Done with Adding/Updating Collections
  destroy the collection size: 6
  deleting model with id: KSc18d06fefddbebd2ade74bcab4c670c907
  deleting model with id: KS07cb95935b1caf3817758739224a3e1a2f
  deleting model with id: KS6f473b3e15740fe7c6c0909e14986700a9
  </code></pre>
  
  <p>What happened? 
  Why did it only do 3?
  How do I debug this?</p>
  
  <p>Any help is appreciated!</p>