Fixes tests and dubious meal form validation.

I found it hard to convert back and forth between weekdays and offsets
(plus it was fragile to the test code, which doesn't guarantee that
games always start on an earlier weekday than they end), so I changed
the date choice field from a weekday to an offset from the game start.
basic, basic styling
less basic styling: colors!

could probably think harder about fonts and table backgrouns, but that requires images
and images require time. TIME.
Merge pull request #148 from jthemphill/meal-fixes

Fixes tests and dubious meal form validation.