title: underscore contains (_.contains) on object types
body: <p>I'm just getting started with Javascript and using the Underscore library.  I see they have all sorts of utility function, like _.contains.  Is there a way to make this work on objects?  </p>
  
  <pre><code>var indexes = [ {'id': 1, 'name': 'jake' }, {'id':4, 'name': 'jenny'},  {'id': 9, 'name': 'nick'}, {'id': 1, 'name': 'jake' }, {'id':4, 'name': 'jenny'} ];
  
  if (_.contains(indexes, {'id':1, 'name': 'jake'})) {
      console.log("contains");
  }
  </code></pre>
  
  <p>Most of the examples they show have simple arrays with strings or numbers in them.  I was wondering what I can do to use their utility functions like _.contains for objects.  Thanks.</p>