title: Add message to formtastic semantic error block
body: <p>If there are semantic errors in the form (mostly from external API), I'd like to add an explanatory message, like so:</p>
  
  <pre><code>&lt;%= semantic_form_for @order, :url =&gt; checkout_purchase_url, :html =&gt; {:class =&gt; 'payment'}, :wrapper_html =&gt; { :class =&gt; "field" }  do |f| %&gt;
  &lt;% if f.has_errors? %&gt;
      &lt;p&gt;There were errors that prevented your order from being submitted.  If you need assistance, please contact us toll-free at &lt;strong&gt;1-800-555-5555&lt;/strong&gt;.&lt;/p&gt;
      &lt;%= f.semantic_errors %&gt;
  &lt;% end %&gt;
  &lt;% end %&gt;
  </code></pre>
  
  <p>However, <code>has_errors?</code> is a protected method.  Is there a way that I can do this?  Thanks.</p>