1. Moving all commands into a Makefile (because we're handling file dependencies, and that's the right tool for it).
2. Ignoring the .html files produced in the root directory for now.
3. Switching to a single layout modeled on that used for workshop websites - will need to update this.

* 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).

This is up for discussion, but at the moment is the
minimal set of files needed to be a Software Carpentry lesson.