The HTML files in the root directory of this repository don't belong in version control,
since they are built from the demonstration files in `pages` rather than from real lessons.
However, the HTML files in the root of actual lessons definitely *do* belong in the repo,
so the `.gitignore` shouldn't ignore them.

1. Modify `.gitignore` to only ignore HTML files in the current directory.
2. Add `_includes/page.html` template.

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.

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