title: Authlogic does not work
body: <p>I have a form which has the following 3 (username, password, email) fields. I would like to validate password and email as per authlogic. But I gonna validate username as per my wish.</p>
  
  <p><strong>html.erb</strong></p>
  
  <pre><code>&lt;%= form_for @author do |f| %&gt;
    &lt;%= f.label :username %&gt;
    &lt;%= f.text_field :username %&gt;
    &lt;%= f.label :password %&gt;
    &lt;%= f.text_field :password %&gt;
    &lt;%= f.label :email %&gt;
    &lt;%= f.text_field :email %&gt;
  &lt;% end %&gt;
  </code></pre>
  
  <p><strong>model.rb</strong></p>
  
  <pre><code> acts_as_authentic                    //to validate (password and email fields)
   acts_as_authentic do |u|
     u.validate_username_field = false //avoid validating username field 
   end
  </code></pre>
  
  <p>This throws the following error. </p>
  
  <pre><code>undefined method `validate_username_field=' for #&lt;Class:0x0000000443cc78&gt;
  </code></pre>
  
  <p>What mistake I am doing here??</p>