Add dow function for getting the day of week of a date
Add functions for red(), green(), blue(), alpha() to return components of a color
Add functions for getting the hue, saturation, lightness and value of a color
Add functions for setting the red, green, blue, alpha, hue, saturation, lightness and value of colors
Merge pull request #1 from nyalldawson/master

Add get/set color component functions, day of week function