title: mongoid update_attributes changed?
body: <p>I want to update_attributes and than check if information is changed</p>
  
  <p>You can simply pass this code to <code>rails console</code> in existing rails + mongoid project</p>
  
  <pre><code>class TestModel
    include Mongoid::Document
    include Mongoid::Timestamps
    field :name, type: String
  end
  
  test = TestModel.new({:name =&gt; "name 1"})
  test.save()
  =&gt; true
  
  test
  =&gt; created_at: 2012-11-14 13:48:26 UTC, updated_at: 2012-11-14 13:48:26 UTC
  
  test.changed?
  =&gt; false
  test.name_changed?
  =&gt; false
  
  test.update_attributes({:name =&gt; "name 2"})
  =&gt; true
  
  test.changed?
  =&gt; false
  test.name_changed?
  =&gt; false
  
  test
  =&gt; created_at: 2012-11-14 13:48:26 UTC, updated_at: 2012-11-14 13:49:23 UTC
  </code></pre>
  
  <p>Am I doing something wrong or this is a bug?</p>