def output_pdf(html, filename)
      html = add_head html
      load_stylesheets
      generate_cover!
      append_stylesheets html
      puts @wkhtmltopdf.command(output_file(filename)).join(' ') if @config.debug
      @wkhtmltopdf.output_pdf html, output_file(filename)
    end
def output_pdf(html, filename)
      html = add_head html
      load_stylesheets
      generate_cover!
      append_stylesheets html
      puts @wkhtmltopdf.command(output_file(filename)).join(' ') if @config.debug
      @wkhtmltopdf.output_pdf html, output_file(filename)
    end
Create the pdf
 @param [String] html the html input
 @param [String] filename the name of the output file