title: field_for and nested form with mongoid
body: <p>Could somebody give me the working example of nested form using mongoid?</p>
  
  <p>My models:</p>
  
  <pre><code>class Employee 
    include Mongoid::Document 
    field :first_name 
    field :last_name 
    embeds_one :address 
  end
  
  class Address 
    include Mongoid::Document 
    field :street 
    field :city 
    field :state 
    field :post_code 
    embedded_in :employee, :inverse_of =&gt; :address 
  end
  </code></pre>