Updated and fixed hugo

I was stuck on an old release of the Hugo static site generator for a while because some of the updated syntax wasn’t trivial to replace. I pulled the trigger this morning and upgraded, and spent the time updating themes and code. Breaking changes between releases are par for the course with Hugo, which does mean I can’t generally recommend it for laypeople. Though to their credit it did manage to find half a dozen posts where I had mangled some frontmatter; in one case from a post from ten y...