def visit_link?(link, from_page = nil)
      !@pages.has_page?(link) &&
      !skip_link?(link) &&
      !skip_query_string?(link) &&
      allowed(link) &&
      !too_deep?(from_page)
    end
def visit_link?(link, from_page = nil)
      !@pages.has_page?(link) &&
      !skip_link?(link) &&
      !skip_query_string?(link) &&
      allowed(link) &&
      !too_deep?(from_page)
    end
Returns +true+ if *link* has not been visited already,
 and is not excluded by a skip_link pattern...
 and is not excluded by robots.txt...
 and is not deeper than the depth limit
 Returns +false+ otherwise.