title: iterate over key-value pairs in the object in sorted order
body: <p>I'd like to iterate over an object</p>
  
  <pre><code>obj = c: 5, a: 10, b: 15
  </code></pre>
  
  <p>in the order based on key, e.g.</p>
  
  <pre><code>_.each obj, (value, key) -&gt; console.log(key, value)
  </code></pre>
  
  <p>to get in the output this</p>
  
  <pre><code># a 10
  # b 15
  # c 5
  </code></pre>
  
  <p>What is the shortest way to do this in CoffeeScript + underscore library?</p>