title: knockout.js: does nesting result in resubscription?
body: <p>Say, we have:</p>
  
  <pre><code>var model = {
      parent: ko.obervable({
          child: ko.observable('')
      })
  };
  </code></pre>
  
  <p>When we call <code>model.parent(newParentValue)</code>, nested <code>child</code> is replacing with new one. Does it result <code>child</code>'s bindings will be unsubscribed from the replaced <code>child</code> and subscribed to the new one?</p>