Add classes to form items to enable theming

We wanted to be able to theme and position and the check box on the registration page. At present there are no classes attached. I made the following changes to the module:

Original
line 143:

    foreach ($lists as $list) {
      if ( variable_get( 'mailchimp_list_'. $list['id'] .'_listtype', '' ) !== 'required' ) {
        $list_form['chimpmail_list_'. $list['id']] = array(
          '#type'           => 'checkbox',
          '#title'          => $list["name"],
          '#default_value'  => variable_get( 'mailchimp_list_'. $list['id'] .'_listtype', '' ) == 'optout' ? true : false,
          '#description'    => variable_get( 'mailchimp_list_'. $list['id'] .'_description', '' ),
        );
      }
    }
    if( $list_form ) {
      $form['chimpmail_lists'] = array(
          '#type'         => 'fieldset',
          '#title'        => t('Newsletter subscriptions'),
          '#weight'       => 5,
          '#collapsible'  => false,

to...

    foreach ($lists as $list) {
      if ( variable_get( 'mailchimp_list_'. $list['id'] .'_listtype', '' ) !== 'required' ) {
        $list_form['chimpmail_list_'. $list['id']] = array(
          '#type'           => 'checkbox',
          '#title'          => $list["name"],
          '#default_value'  => variable_get( 'mailchimp_list_'. $list['id'] .'_listtype', '' ) == 'optout' ? true : false,
          '#description'    => variable_get( 'mailchimp_list_'. $list['id'] .'_description', '' ),
          '#prefix'         => '<div class="mailchimp-sub-check">',
          '#suffix'         => '</div>',
        );
      }
    }
    if( $list_form ) {
      $form['chimpmail_lists'] = array(
          '#type'         => 'fieldset',
          '#title'        => t('Newsletter subscriptions'),
          '#weight'       => 5,
          '#collapsible'  => false,
          '#prefix'       => '<div class="mailchimp-form">',
          '#suffix'       => '</div>',

So basically just adding #prefix and #suffix to the fieldset and the checkbox. Would be great to slip these, and maybe some others, into the next release to enable theming.

Cheers,
Neil