title: Mongoid embeds_many with default order
body: <p>How can I set default order to my embeded objects, like:</p>
  
  <pre><code>class Post
    embeds_many :comments, :order =&gt; "author"
    accepts_nested_attributes_for
  end
  </code></pre>
  
  <p>Now I handle it with passing order straight:</p>
  
  <pre><code>f.fields_for :comments, @post.comments.asc(:author) do |comment|
    ...
  end
  </code></pre>