title: select_tag options_for_select, default value not getting set
body: <p>the rendered html:</p>
  
  <pre><code>&lt;select id="version_filter" name="version_filter"&gt;
  &lt;option value="2"&gt;Current Version&lt;/option&gt;
  &lt;option value="1"&gt;1&lt;/option&gt;
  &lt;option value="0"&gt;0&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>the select_tag</p>
  
  <pre><code>&lt;%= select_tag "version_filter", 
          options_for_select(@version_select, @selected_version.to_s) %&gt;
  </code></pre>
  
  <p>I through an alert into my page to see if the @selected_version even exists:</p>
  
  <pre><code>alert("&lt;%= @selected_version.to_s %&gt;");
  </code></pre>
  
  <p>and it does. the @selected_version is 0, but when the page loads, the drop down select thing shows "Current Version" as the selected value.</p>
  
  <p>Rails isn't complaining about the syntax, so, how do I get not-the-first-value to be the defaultly selected?</p>