title: Mongoose-Paginate - Sorting by a populated field
body: <p>I am using mongoose-paginate to get a list of records sorted by a field which was populated from a reference.</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>// models
  
  const Company = new Schema({
    name: String,
    type: String
  });
  
  const report = new Schema({
    _company: { 
      type: String, 
      ref: 'Company' 
    },
    name: String
  });
  
  let options = {
    offset: 0,
    limit:10,
    populate: '_company',
    select: 'type _company',
    sort: { '_company.name': 1 },
    lean: true
  };
  
  // paginate.
  report.paginate({},options, (err, results) =&gt;  {
    if(err) {
      console.log(err);
    }
    
    res.jsonp({
      data: results
    });
  })</code></pre>
  </div>
  </div>
  </p>
  
  <p>Is there a way to sort by the field _company.name, which is a populated field.</p>
  
  <p>added sample code below.</p>
  
  <p>Thanks.</p>