Display the css classes on the form elements

If you add this function to the module it should add the css class to the form as well as the display.

function field_formatter_class_field_widget_form_alter(&$element, &$form_state, $context) {
  $css_class = $form_state['field']['field_email_address'][LANGUAGE_NONE]['instance']['display']['default']['settings']['field_formatter_class'];
  if(!empty($css_class)) {
    if(empty($element['value']['#attributes'])) {
      $element['value']['#attributes'] = array();
    }
    if(empty($element['value']['#attributes']['classes'])) {
      $element['value']['#attributes'] = array();
    }

    $element['value']['#attributes']['class'][] = $css_class;
  }
}

The reason you would want to do this is incase you are using this module in conjunction with the entityform module.