title: MongoDB find() order child objects
body: <p>I know that I can use $orderBy when doing a find() on a collection.  But My collection contains other objects, how can I sort those objects?  For instance:</p>
  
  <pre><code>books: [{
    title: 'book 1',
    authors: [
       { name: 'jim' },
       { name: 'bob' },
    ]
  }, {
    title: 'book 2',
    authors: [
       { name: 'steve' },
       { name: 'joe' },
    ]
  }];
  </code></pre>
  
  <p>I want to do db.collections.find();  and have it return all books in order (which I know how to do using $orderBy, but I also want the authors sorted.</p>