kepstin/0x40hues-html5

Improve various places that were relying on heavy DOM updates, or which
performed synchronous! reflow.

In particular, this re-uses the same elements when updating hue name,
song title, image name; calculates which font size to use based on a
value calculated at startup rather than by doing reflow, and reduces the
frequency of canvas size checks (was every frame) to only on detected
window resizes.