Handle CSSUnits in garden.color/hsl
Add clip fn to util ns
Fix bug in hue->rgb that was creating high green values
Correction to exception message, lightness not luminosity
Fix cyclic load dependecy, drop java.awt.Color support (for now)
Add several new color functions

Most of these functions are borrowed from Sass but a few have been
added for convenience. The functions as-hex, as-rgb, and as-hsl still
need an else clause before the next version as noted.