Move docs to wiki

- [ ] index in the sidebar
- [ ] TOC in the header
- [ ] path track in the footer

some links:
- [add wiki as a submodule](http://brendancleary.com/2013/03/08/including-a-github-wiki-in-a-repository-as-a-submodule/)
- [generate index to sidebars](https://github.com/hybridgroup/GitHub-Wikifier)