Change to kramdown as per GitHub's warning message

https://help.github.com/articles/updating-your-markdown-processor-to-kramdown/

Emails follows:

The page build completed successfully, but returned the following warning:

You are currently using the Textile markup language, which is no longer
supported by GitHub Pages and may cease working at any time. To ensure your
site continues to build, you must use Markdown (or HTML) to author your conent
by converting all `.textile` files within your repository to Markdown (`.md`).
For more information, see
https://help.github.com/articles/updating-your-markdown-processor-to-kramdown.

For information on troubleshooting Jekyll see:

  https://help.github.com/articles/troubleshooting-jekyll-builds

  If you have any questions you can contact us by replying to this email.

Author: markburns

_config.yml

@@ -1,3 +1,4 @@
 redcloth:
   hard_breaks: false
 exclude: ["ebooks", "script", "original_repo", "Gemfile", "Gemfile.lock", "dictionary.txt", "README.md"]
+markdown: kramdown