def to_htmls(files, options = {})
      FileUtils.chdir(File.expand_path(options[:base_dir]))
      files.each_with_index do |file, index|
        puts "FYI: process file #{index + 1} of #{files.size} : #{file}"
        to_html(file, options)
      end
    end
def to_htmls(files, options = {})
      FileUtils.chdir(File.expand_path(options[:base_dir]))
      files.each_with_index do |file, index|
        puts "FYI: process file #{index + 1} of #{files.size} : #{file}"
        to_html(file, options)
      end
    end
convert multiple files to html