find_first_href (OpenID)

    # File lib/openid/consumer/html_parse.rb, line 120
      def OpenID.find_first_href(link_attrs_list, target_rel)
        # Return the value of the href attribute for the first link tag in
        # the list that has target_rel as a relationship.

        # XXX: TESTME
        matches = find_links_rel(link_attrs_list, target_rel)
        if !matches or matches.empty?
          return nil
        end

        first = matches[0]
        return first['href']
      end