* switch from jekyll to mkdocs.
* fix footer.
* fix some minor layout bugs
* fix html bug in the page.
* add sample code
* ignore mkdocs built site folder.
* fix link check
* move the theme inside docs folder
* fix link to about page in the footer.
* Fix broken links and re-gen docs.
Still debugging the active state for learn sidenav. When you click on anything under API, it should stay open. Chris, you will find some debugging code in there, but feel free to erase & start over. Current sidebar logic is directly in layouts/reference.html.
Related work items: #2164
Pantazis Deligiannis
Chris Lovett