title: Change html form id generated by form_for rails 3.1
body: <p>I have this form_for:</p>
  
  <pre><code>&lt;%= form_for [post, Comment.new,], :remote =&gt; true do |f| %&gt;
  &lt;%= f.text_area :content, :cols =&gt;10, :rows =&gt; 1%&gt;
  &lt;% end %&gt;
  &lt;%= f.submit :class =&gt; "input_comment"  %&gt;
  </code></pre>
  
  <p>That generate the next code html:</p>
  
  <pre><code>&lt;form method="post" id="new_comment" data-remote="true" class="new_comment" 
  action="/post/4efcda9e1d41c82486000077/comments" accept-charset="UTF-8"&gt;&lt;div 
  style="margin:0;padding:0;display:inline"&gt;&lt;input type="hidden" value="✓" name="utf8"&gt;
  &lt;input type="hidden" value="ctVfDF/O4FIR91I7bC5MVezQmutOCkX3dcXe73uNPZY=" name="authenticity_token"&gt;
  
  &lt;textarea rows="1" name="comment[content]" id="comment_content" cols="10"&gt;&lt;/textarea&gt;
  &lt;input type="submit" value="Create Comment" name="commit" class="input_comment"&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>If I have many forms in a same page is not a html valid with the same id.</p>
  
  <ul>
  <li>The id for form_for generate <strong>id="new_comment"</strong></li>
  <li>The id for textarea generate <strong>id="comment_content"</strong></li>
  </ul>
  
  <p>With so many forms in a same page is not valid html.</p>
  
  <p><strong>How can I change the id autogenerate by form_for method helper from rails 3.1?</strong></p>