title: Populate nested array in mongoose
body: <p>How can I populate "components" in the example document:</p>
  
  <pre><code>  {
      "__v": 1,
      "_id": "5252875356f64d6d28000001",
      "pages": [
        {
          "__v": 1,
          "_id": "5252875a56f64d6d28000002",
          "page": {
            "components": [
              "525287a01877a68528000001"
            ]
          }
        }
      ],
      "author": "Book Author",
      "title": "Book Title"
    }
  </code></pre>
  
  <p>This is my JS where I get document by Mongoose:</p>
  
  <pre><code>  Project.findById(id).populate('pages').exec(function(err, project) {
      res.json(project);
    });
  </code></pre>