code_tag.rb

module Jekyll
  class CodeTag < Liquid::Tag

    def initialize(tag_name, text, tokens)
      super
      @language = text
    end

    def render(context)
      "<pre data-language='#{@language}'><code>"
    end
  end
end

module Jekyll
  class CodeEndTag < Liquid::Tag

    def initialize(tag_name, text, tokens)
      super
    end

    def render(context)
      "</code></pre>"
    end
  end
end

Liquid::Template.register_tag('code', Jekyll::CodeTag)
Liquid::Template.register_tag('endcode', Jekyll::CodeEndTag)