title: Add class attribute to Form Errors
body: <p>I´m developing an application using Zend Framework 2 and I use <strong>FormRow</strong> helper to render a label, the input and errors (if present) in a Form.</p>
  
  <pre><code>//within the view
  echo $this-&gt;formRow($form-&gt;get('Name'));
  </code></pre>
  
  <p>When a user submits the form without filling the required input text field FormRow render´s it with the following error message:</p>
  
  <pre><code>&lt;label&gt;
      &lt;span&gt;Name: &lt;/span&gt;
      &lt;input class="input-error" type="text" value="" placeholder="Insert Name Here" name="Name"&gt;
  &lt;/label&gt;
  &lt;ul&gt;
      &lt;li&gt;Value is required and can't be empty&lt;/li&gt;
  &lt;/ul&gt;
  </code></pre>
  
  <p>How can I set a class for the <strong>li</strong> tag to style it afterwards?</p>
  
  <p>I know that I can echo the formElementErrors with the desired class attribute via.. </p>
  
  <pre><code>&lt;?php echo $this-&gt;formElementErrors($form-&gt;get("Name"), array('class' =&gt; "valuerequired", 'message' =&gt; "errortestmessage")); ?&gt;
  </code></pre>
  
  <p>..but FormRow will still render the error message without the class.</p>
  
  <p>Just for reference I´m setting the entity this way:</p>
  
  <pre><code>public function getInputFilter()
      {
          if (!$this-&gt;inputFilter) {
              $inputFilter = new InputFilter();
  
              $factory = new InputFactory();
  
              $inputFilter-&gt;add($factory-&gt;createInput(array(
                  'name'     =&gt; 'Name',
                  'required' =&gt; true,
                  'filters'  =&gt; array(
                      array('name' =&gt; 'StripTags'),
                      array('name' =&gt; 'StringTrim'),
                  ),
                  'validators' =&gt; array(
                      array(
                          'name'      =&gt; 'StringLength',
                          'options' =&gt; array(
                              'encoding' =&gt; 'UTF-8',
                              'min'      =&gt; 1,
                              'max'      =&gt; 100,
                          ),
                      ),
                  ),
             )));
  
              $this-&gt;inputFilter = $inputFilter;
          }
          return $this-&gt;inputFilter;
      }
  </code></pre>