title: How can I observe array changes and see which new element is added?
body: <pre><code>onArrayChanged: function(obj, keyName, value) {
  
      // What is value here, exactly?
  
  }.property('array.@each')
  </code></pre>
  
  <p>When an element is added to the array, how do I know which value was added? LIkewise, when a value is removed from the array, how do I access that?</p>