title: How do I use the comparator to sort by multiple attributes?
body: <p>I want to be able to sort my models in a collection first by their <code>required</code> flag and then <code>value</code> alphabetically.</p>
  
  <p>Currently my code looks like to this:</p>
  
  <pre><code>var myModel = Backbone.Model.extend({
      defaults: {
          required: true,
          value: '',
          ...
      }
  };
  
  var myCollection = Backbone.Collection.extend({
      model: myModel,
      comparator: function (model) {
          return -model.get('required');
      }
  });
  
  myCollection.create([
       {value: 'A', required: false},
       {value: 'B', required: true},
       {value: 'C', required: false},
       {value: 'D', required: false},
       {value: 'E', required: true}
  ]);
  </code></pre>
  
  <p>The comparator sorts my models by required first but I'm at a loss as to how to also sort them alphabetically. Currently when the view renders them they come out</p>
  
  <p><code>E, B, D, C, A</code></p>
  
  <p>I want them to be rendered:</p>
  
  <p><code>B, E, A, C, D</code></p>