title: Grouped Select in Rails
body: <p>Simple question really - how do I use the select(ActionView::Helpers::FormOptionsHelper) with grouped options?</p>
  
  <p>I have got it working with a select_tag (ActionView::Helpers::FormTagHelper) but I would really like to have it using a select tag to match the rest of the form.  Is this possible?</p>
  
  <p>My options look like this:</p>
  
  <pre><code>[
    ['Group 1', ["Item 1", "Item 2", "Item 3"]],
    ['Group 2',["Item 1", "Item 2", "Item 3", "Item 4"]]
  ]
  </code></pre>
  
  <p>whilst my view is currently:</p>
  
  <pre><code>%tr#expense
    %td
      = f.text_field :value
      = f.hidden_field :type, :value =&gt; mode
  </code></pre>