title: Count number of keys in object with Coffeescript
body: <p>I would like to know how many keys are in my coffeescript object.</p>
  
  <p>I can do it with this in js:</p>
  
  <p><code>Object.keys(obj).length</code></p>
  
  <p>Is there a way to do this in Coffeescript?</p>