title: updating sub object in mongodb
body: <p>Consider following entry in my mongo collection.</p>
  
  <pre><code>{
    "id" : "_0001",
    "map" : {
              "foo" : 1
            }
  }
  </code></pre>
  
  <p>Now i need to add an entry to inside map. like</p>
  
  <pre><code>{
    "id" : "_0001",
    "map" : {
              "foo" : 1,
              "bar" : 2,
            }
  }
  </code></pre>
  
  <p><code>map</code> is not a <code>list</code> so i cannot use <code>$push</code> there. Is there any way of doing this in mongo. And also I'm accessing the database via casbah. Please note down the casbah codes if you can.</p>
  
  <p>NOTE:- <strong>map should not be a list</strong></p>