DateMath: properly recognize and handle weeks.

Fixes #628.
Merge pull request #629 from mwmiller/date_math

DateMath: properly recognize and handle weeks.
Move goodies to new styling mechanism.

- Rename 'style.css' to appropriate ID-based name.
- Remove explicit inclusion of CSS, as it will now be auto-included.
- Update tests which explicitly checked for styling.
SHA: move from inline CSS.
ValarMorghulis: move from inline CSS.
Dice: move from inline CSS.
Unifornify: move from inline CSS.
UltimateAnswer: remove trailing whitespace.
UltimateAnswer: move from inline css
ColorCodes: move from inline css
ResistorColors: move from inline CSS.