title: underscore-contrib can't use the _.snapshot function
body: <p>I'm using the underscore.js library (version 1.8.3) on my project, on one of the scripts I needed to deep clone an object, because the _.clone(obj) function only does a shallow clone, I've added the underscore-contrib (version 0.3.0) library I grabbed from the source repo</p>
  
  <pre><code>&lt;script type="text/javascript" src="underscore-min.js"&gt;&lt;/script&gt;
  &lt;script type="text/javascript" src="underscore-contrib.min.js"&gt;&lt;/script&gt;
  </code></pre>
  
  <p>and attempted to use the _.snapshot(obj) function like so</p>
  
  <pre><code>var clonedData = _.clone(data); // works 
  var snapshotData = _.snapshot(data); // doesn't work
  </code></pre>
  
  <p>It didn't work, the console shows</p>
  
  <pre><code>TypeError: _.snapshot is not a function
  </code></pre>
  
  <p>Eventually I tried to "hack it", I've copy pasted the function contents from the development version into a function in my script and it worked fine, but It's kind of ugly, I want to avoid the duplication and use it properly. what am I missing ? </p>