Apply 'alert' role to response area. ref) http://wordpress.org/support/topic/better-accessibility-error-and-success-messages-in-contact-form-7?replies=7

git-svn-id: https://plugins.svn.wordpress.org/contact-form-7/trunk@816904 b8457f37-d9ea-0310-8a92-e5e31aec5664