def flattr_button(site, page = nil)
      return if site['flattr_uid'].nil?

      keys = %w[url title description uid popout button category language tags]
      options = flattr_options(site, page, keys)

      button =  '<a class="FlattrButton" style="display:none;" '
      button << %Q{title="#{options.delete('title')}" href="#{options.delete('url')}" }
      button << options.map { |k, v|
        %Q{data-flattr-#{k}="#{v}"} unless k == 'description'
      }.join(' ')
      button << ">\n\n#{options['description'].gsub(/<\/?[^>]*>/, "")}\n</a>"
    end
def flattr_button(site, page = nil)
      return if site['flattr_uid'].nil?

      keys = %w[url title description uid popout button category language tags]
      options = flattr_options(site, page, keys)

      button =  '<a class="FlattrButton" style="display:none;" '
      button << %Q{title="#{options.delete('title')}" href="#{options.delete('url')}" }
      button << options.map { |k, v|
        %Q{data-flattr-#{k}="#{v}"} unless k == 'description'
      }.join(' ')
      button << ">\n\n#{options['description'].gsub(/<\/?[^>]*>/, "")}\n</a>"
    end
Returns a flattr button

   {{ site | flattr_button:page }}