title: Custom data-attributes from select_tag not submitting - Rails 4
body: <p>I have a simple search form_tag in a Rails 4 app.</p>
  
  <p>One of the options is a select_tag:</p>
  
  <pre><code>&lt;%= select_tag "plottable[plottable_id]", options_for_select(Plottable.all.map{ |plottable| [ plottable, plottable.id, { 'plottbale-type' =&gt; plottable.class } ] }), prompt: 'Select one option'%&gt;
  </code></pre>
  
  <p>The HTML is generated properly, resulting in:</p>
  
  <pre><code>&lt;select name="plottable[plottable_id]" id="plottable_plottable_id"&gt;
    &lt;option value=""&gt;Select one option&lt;/option&gt;
    &lt;option plottable-type="Pool" value="3"&gt;Pool1&lt;/option&gt;
    &lt;option plottable-type="Pool" value="4"&gt;Pool2&lt;/option&gt;
    &lt;option plottable-type="Asset" value="33"&gt;Asset1&lt;/option&gt;
    &lt;option plottable-type="Asset" value="34"&gt;Asset2&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>When submitting the form the plottable-type does not get submitted. Here are the params:</p>
  
  <pre><code>Parameters: {"utf8"=&gt;"✓", "from_time"=&gt;"", "to_time"=&gt;"", "plottable"=&gt;{"plottable_id"=&gt;"35"}, "commit"=&gt;"Search"}
  </code></pre>
  
  <p>Thanks for your suggestions.</p>