title: ERB: add class to url_for with condition
body: <p>I'm creating a page with refinery which has multiple languages.
  Now i want to add a language Switch and don't know how to do the followung:</p>
  
  <pre><code>&lt;%= link_to 'DE', url_for( :locale =&gt; 'de' ), :class =&gt; "selected" %&gt;
  </code></pre>
  
  <p>The selected should only be there if</p>
  
  <pre><code>I18n.locale == 'de'
  </code></pre>
  
  <p>I could do the following but that is a bit too much repetition and despite that it doesn't work, even tough i don't know why:</p>
  
  <pre><code>I18n.locale == 'de' ? link_to('DE', url_for( :locale =&gt; 'de' ), :class =&gt; "selected") : link_to('DE', url_for( :locale =&gt; 'de' ))
  </code></pre>
  
  <p>So how can i do this?</p>