title: Mongoose update embedded document does not work
body: <p>Greeting all,</p>
  
  <p>I defined a deeply embedded mongoose model "Person", which contains a field "Contact", and "Contact" has an array of "Address" for this person's work, home, delivery etc addresses. </p>
  
  <p>When I wanted to update an address, and use the model's "save" function, the change wasn't reflected in the database. </p>
  
  <pre><code>            console.log(person.Contact.Address[i].City = 'Chicago');
              person.save(function (err) {
                  if (!err) {
                     console.log(person.Contact.Address[i].City);
  </code></pre>
  
  <p>The console.log indicates that the field City has been updated to new value, but the mongodb's value stays the same. </p>
  
  <p>Could you please help me with this issue?</p>
  
  <p>Thanks!
  Gary</p>