def anchor_text(heading_text)
      text = nameize(strip_html_tags(heading_text))
      text_with_suffix = text
      i = 2
      while @heading_anchors[text_with_suffix]
        text_with_suffix = "#{text}-#{i}"
        i+=1
      end
      @heading_anchors[text_with_suffix] = true
      text_with_suffix
    end
def anchor_text(heading_text)
      text = nameize(strip_html_tags(heading_text))
      text_with_suffix = text
      i = 2
      while @heading_anchors[text_with_suffix]
        text_with_suffix = "#{text}-#{i}"
        i+=1
      end
      @heading_anchors[text_with_suffix] = true
      text_with_suffix
    end
returns anchor text from heading text.
 e.g. First Heading! => first-heading

 if there are duplicates, they get numbered:
   heading => heading
   heading => heading-2
   heading => heading-3