CSS: switch to monospace

CSS: switch to monospace

Safari badly misdisplays Bedstead in proportional mode.  This is
caused by a bug in WebKit, and I haven't found an acceptable
workaround.  Thus, I think the best thing to do is to turn off
proportional spacing on the Web page entirely.  I think it looks nice,
but even I'll admit that it's a little too tight, and I know others
prefer the monospaced version.

Also, I can't think of a way that a real chip anything like the
SAA5050 could produce proportionally-spaced text.  It's fundamentally
based on getting fed character data at a constant 1 MHz.  There's no
way it can ask for a character early because the previous one was
narrow.