Revert root color and background normalization

Commit: 907890983eb2d6667e4b9cbd8bd03ead4b077e34

The change caused problems with `body` background color no longer
bubbling up the the `html` element.

It also prevented you from setting `color` or `background` styles on
`html` before the normalize.css styles.

It might not be possibly to safely address – within normalize.css –
the problem that it was trying to avoid.

Fix gh-188