滤器category_link 所以WordPresscreates 删除类别的URL，以及redirect_canonical 所以它accepts 这些URL：

add_filter( \'category_link\', \'wpse_71666_trailingslash_cat_url\' );
add_filter( \'redirect_canonical\', \'wpse_71666_trailingslash_cat_url\', 20, 2 );

function wpse_71666_trailingslash_cat_url( $url, $request = \'\' )
{
    if ( \'category_link\' === current_filter() )
        return rtrim( $url, \'/\' ) . \'/\';

    if ( "$url/" === $request and is_category() )
        return $request;

    return $url;
}