title: In Mongoose (mongodb node.js), how to update existing values and insert missing, without removing unspecified values?
body: <p>I'm trying to maintain an instantaneous statistics block, e.g.;</p>
  
  <pre><code>model = {
    id: 123,
    stats: {
      fooCount: 117,
      barCount: 175,
      bazCount: 654
    }
  }
  </code></pre>
  
  <p>...and be able to update an existing record, but only specify the <em>new</em> values, like this:</p>
  
  <pre><code>model.update({
    '_id': 123,
      stats: {
        fooCount: 118 
      }
  });
  </code></pre>
  
  <p>...without blowing away the old values in <code>stats</code>.  Is this possible without writing too much more code around my updates?</p>