title: can findOneAndUpdate trigger schema post update/save?
body: <p>I am stuck with socket io with problem emit the changes. Just wondering is there a way to trigger scheme.post update or save. at the moment scheme.post save doesn't work with <strong>findOneAndUpdate</strong>, please help out been stuck for hrs... any help much appreciated.</p>
  
  <pre><code>  project.schema.post('update', function (doc) {
      onSave(socket, doc);
    });
    project.schema.post('save', function (doc) {
      onSave(socket, doc);
    });
  </code></pre>
  
  <p>where does the udate</p>
  
  <pre><code>project.findOneAndUpdate(
      { 
        _id: req.body._id 
      },
      { $set: 
        { 'watchers' : req.body.watchers }
      },
      function(err, data) {
        return res.json(200, data)
      }
    );
  </code></pre>