def link(text, url = nil)
      url = text if url.nil?
      tag(:a, text, href: url)
    end
def link(text, url = nil)
      url = text if url.nil?
      tag(:a, text, href: url)
    end
Write a link
 <tt>text</tt> The text in the link
 <tt>url</tt> The url to link to.