save css files when using save_and_open_page in capybara

capybara_save_css.rb

module Capybara
  class Session

    def save_page(path=nil)
      body = rewrite_css_and_image_references(html)
      path ||= "capybara-#{Time.new.strftime("%Y%m%d%H%M%S")}#{rand(10**10)}.html"
      path = File.expand_path(path, save_folder_path)

      FileUtils.mkdir_p(File.dirname(path))

      File.open(path,'w') { |f| f.write(body) }
      path
    end

    private

    def rewrite_css_and_image_references(response_html) # :nodoc:
      return response_html unless Capybara.app_host.present?
      directories = Dir.new(Rails.root.join("app/assets")).entries.inject([]) do |list, name|
        list << name if File.directory?(name) and not name.to_s =~ /^\./
        list
      end
      response_html.gsub(/("|')\/(#{directories.join('|')})/, '\1' + Capybara.app_host + '/\2')
    end

    def save_folder_path
      Capybara.save_and_open_page_path.present?? Capybara.save_and_open_page_path : "tmp/capybara"
    end

  end
end