Set same value

[andsnpl]

Color objects are able to mutate even thought the values given are not different than existing ones, as in the following example:

var color = Color('#abc');
color.hexString(); // -> '#AABCC'
color.hue(color.hue()).hexString() // -> '#A9BACB'

I've added a new test, and a patch on Color.prototype.setChannel() that gets the test to pass.

[MoOx]

Hum weird. Thanks for the fix. I will try to cut a new release soon with immutable colors, cause mutation produce a lot of unexpected behavior (ref #56)