title: Eloquent where condition based on a "belongs to" relationship
body: <p>Let's say I have the following model:</p>
  
  <pre><code>class Movie extends Eloquent
  {
      public function director()
      {
          return $this-&gt;belongsTo('Director');
      }
  }
  </code></pre>
  
  <p>Now I'd like fetch movies using a where condition that's based on a column from the directors table.</p>
  
  <p>Is there a way to achieve this? Couldn't find any documentation on conditions based on a belongs to relationship.</p>