add callback-cockles theme
just review octopress structure

1. source

   * _include:

      custom -- head, header, navigation and foot can modofy
      post   -- content of post(author date and share)
      aside  -- recend_posts, github  and so on

   * _layout: templete for show post

   * other:

      maybe a lot of subdirect have not understand what is it?
    just learn!!