Bringing titles into line with latest version of template

W. Trevor King: I've cherry-picked this from 375ba558 (Bringing titles
into line with latest version of template, 2014-12-20, [1]), because I
think it's worth keeping as much auto-generated content out of this
branch as possible, and I don't want to develop based on
shell-novice/gh-pages with it's in-tree HTML.

[1]: https://github.com/swcarpentry/shell-novice/commit/375ba558183b2bfa68d095eb3b0e2d23af705efa