title: Create a select tag with some options grouped and others not grouped
body: <p>I'm using Rails 3. I want to create a select tag with some options grouped and others not grouped. Options would look something like this:</p>
  
  <pre><code>Income
  Auto
    Fuel
    Maintenance
  Home
    Maintenance
    Mortgage
  </code></pre>
  
  <p>In this example, Income is not a group, but Auto and Home are. </p>
  
  <p>I see three helper methods <code>grouped_options_for_select</code> and <code>grouped_collection_select</code>, <code>option_groups_from_collection_for_select</code> but they all appear to require that you have a group for every option.</p>
  
  <p>Is there a way to use a helper to do this or will I have to generate the HTML myself? I imagine I could use two different helpers to create the options and just append the results of both.</p>