title: add onsubmit attribute to form and submit it
body: <p>I have two buttons on page:</p>
  
  <pre><code>&lt;div class="bottons"&gt;
          &lt;button class="wiz_button wizard_prev_step" type="button" style="margin-top: 27px;
              display: none"&gt;&lt;span&gt;&lt;span&gt;Previous&lt;/span&gt;&lt;/span&gt;&lt;/button&gt;
          &lt;form id="orderForm" method="POST"&gt;
          &lt;input type="hidden" name="Signed_Order_B64" value=""&gt;
          &lt;input type="hidden" name="email" size="50" maxlength="50" value=""&gt;
          &lt;input type="hidden" name="Language" value="rus"&gt;
          &lt;input type="hidden" name="firstname" value=""&gt;
          &lt;input type="hidden" name="surname" value=""&gt;
          &lt;input type="hidden" name="appendix" value=""&gt;            
          &lt;button class="wiz_button wizard_next_step disabled long" type="button" style="margin-top: 27px;"&gt;
              &lt;span&gt;&lt;span&gt;Next&lt;/span&gt;&lt;/span&gt;&lt;/button&gt;
          &lt;/form&gt;
      &lt;/div&gt;
  </code></pre>
  
  <p>This buttons from my custom wizard. Also, I have a click event handler for <code>Next</code> button:</p>
  
  <pre><code>$('.wizard_next_step').click(function () {
  // load next step and other stuff
  })
  </code></pre>
  
  <p>I want when user locate on the last step the post form:</p>
  
  <pre><code>if (currentStep === '3') {
  // here I want set onsubmit function for the form  *
  }
  </code></pre>
  
  <p>How can I do this?<br>
  Thanks.</p>
  
  <p>PS. The solution must works in IE 7 and above.</p>