adds to excerpt tiny emc editor

/**
 * Replaces the default excerpt editor with TinyMCE.
 */
class T5_Richtext_Excerpt
{
    public static function switch_boxes()
    {
        if ( ! post_type_supports( $GLOBALS['post']->post_type, 'excerpt' ) )
        {
            return;
        }

        remove_meta_box(
            'postexcerpt'
        ,   ''
        ,   'normal'
        );

        add_meta_box(
            'postexcerpt2'
        ,   __( 'Excerpt' )
        ,   array ( __CLASS__, 'show' )
        ,   null
        ,   'normal'
        ,   'core'
        );
    }

    public static function show( $post )
    {
    ?>
        <label class="screen-reader-text" for="excerpt"><?php
        _e( 'Excerpt' )
        ?></label>
        <?php
        wp_editor(
            self::unescape( $post->post_excerpt ),
            'excerpt',
            array (
            'textarea_rows' => 15
        ,   'media_buttons' => FALSE
        ,   'teeny'         => TRUE
        ,   'tinymce'       => TRUE
            )
        );
    }

    public static function unescape( $str )
    {
        return str_replace(
            array ( '&lt;', '&gt;', '&quot;', '&amp;', '&nbsp;', '&amp;nbsp;' )
        ,   array ( '<',    '>',    '"',      '&',     ' ', ' ' )
        ,   $str
        );
    }
}