fix Reddit share URL; driveby star, driveby trim dead code

I would have thought the SITEURL template variable would faithfully
reflect my Pelican SITEURL setting, but instead it was getting
populated as "../../.."?! (A relative-URLs setting??—the root is
"three levels up" from `YYYY/Mon/post-slug/`.) Hardcoding it should be
fine; the site isn't going anywhere (until the virus kills me).

While we're here, get that disgraceful hyphen out of the page
title. And, prune some conditional markup that misled my past self
into thinking that SITEURL would work.