title: Why is it not possible to add the same modifier to the context twice?
body: <p>I've been playing around with the positioning Famo.us course:
  <a href="http://famo.us/university/famous-101/positioning/" rel="nofollow">http://famo.us/university/famous-101/positioning/</a></p>
  
  <p>On page 4 they talk about chaining modifiers.  Why is it not possible to reuse the same modifier more than once?  </p>
  
  <p>I tried the following code from the example:</p>
  
  <pre><code>mainContext
    .add(translateModifierOne)
    .add(rotateModifierOne)
    .add(redSurface);
  
  mainContext
    .add(rotateModifierTwo)
    .add(rotateModifierOne)
    .add(translateModifierTwo)
    .add(greySurface);
  
  mainContext
    .add(rotateModifierTwo)  
    .add(greySurface);
  </code></pre>
  
  <p>Inspecting the DOM, I only see a single .</p>
  
  <p>Thanks,</p>
  
  <p>JD</p>