title: Initialize model with a default attribute that assigns from other attribute
body: <p>The Time model has two defaults attributes duration and remainingTime and I need that remainigTime values will depend to the duration.</p>
  
  <pre><code>class Time extends Backbone.Model
      defaults:
        duration: 0
        remainingTime: @duration  //This don't work
  </code></pre>
  
  <p>How can I access duration value for assign it to remainingTime?</p>
  
  <p>PD: In addition I tested with <code>Time.duration, Time.defaults.duration, this.duration</code></p>