* documents all key-bindings and mouse-bindings. (e.g. spotlight)
* support centering in table cell.
* [BUG]: PDF slide doesn't scale???
* improve Clutter support.
* support GStreamer.
* support MeCab for clever wrapping.
* support SilverCity or CodeRay.
* [nori] write manpage (converted from something like RD or DocBook XML).
* support GooCanvas.
* support Nokogiri as alternative of HTree.
* support theme configuration in RD:
  e.g.:

    : theme
       * @slide_footer_info_left_text = "Ruby Kaigi"
       * image_path: clear-code-images
       * @slide_logo_image = "clear-code-logo.png"
       * clear-blue

    ->
      @slide_footer_info_left_text = "Ruby Kaigi"
      add_image_path("clear-code-images")
      @slide_logo_image = "clear-code-logo.png"
      include_theme("clear-blue")

