code: def add_checkin_comment(checkin_id, options={})
        response = connection.post do |req|
          req.url "checkins/#{checkin_id}/addcomment", options
        end
        return_error_or_body(response, response.body.response)  
      end
docs: Add a comment to a checkin.
  
   @param [String] checkin_id the ID of the checkin.
   @param [Hash]  options
   @option options String :text - Text of the comment to add, 200 character max.