1.  Explaining how to use GitHub import instead of creating a repository manually.
2.  Explaining the difference between `lesson-template` and `lesson-example`.

* Add `.nojekyll` to stop GitHub trying to compile.
* Get rid of Jekyll `_config.yml`.
* Create placeholder `css` and `img` directories.
* Create `pages` directory with source for web pages.
* Move all Markdown files into `pages`.
* Move `tools` into `pages` (because that's where people will mostly work).
* Move `_includes` and `_layouts` into `pages` (because that's where we'll compile).