Add link back to post from comment "thank you" page

[Sequoia]

Possibilities

• <A href="javascript:window.location.back()">Go Back</a> verify this works after redirect
• change redirect_to hidden field to go back to post
  • add ?comment-submitted to URL
  • read from URL via JS
  • add "thanks for comment" message
• add "go back" link as above, append the ?goback=http://url/post-slug to redirect_to
  • read from URL via JS
  • Fix link to redirect back to post