Documentation uses redcarpet for rendering Markdown, not kramdown

[StevenMaude]

Received a page build warning:

You are currently using the 'redcarpet' Markdown engine, which is no longer supported by GitHub Pages and may cease working at any time. To ensure your site continues to build, remove the 'markdown' setting in your site's '_config.yml' file and confirm your site renders as expected. For more information, see https://help.github.com/articles/updating-your-markdown-processor-to-kramdown.

There are several extensions enabled, don't know what kramdown settings replicate these.

See also GitHub's notes.