title: Document class_attribute with yard
body: <p>How do I tell yard to document class attributes that are set up with Rails' <a href="http://apidock.com/rails/Class/class_attribute" rel="nofollow"><code>class_attribute</code> method</a>? Currently it's just ignoring them.</p>
  
  <p>An example:</p>
  
  <pre><code>class Base
    class_attribute :defaults
  
    self.defaults = { foo: 'bar' }
  end
  </code></pre>