Added lib/hue/rgb.rb lib/hue/hexrgb.rb and lib/hue/hsl.rb

Implements Issue #6

These classes allow you to generate the HUE color values from 3 different formats.
````ruby
RGB.new(123,231,222).to_hue
HexRGB.new("7BD5DE").to_hue
HSL.new(185.45, 0.60, 0.67).to_hue
````
They each return a hash in the format of: ````{:hue=>33760, :saturation=>153, :luminance=>172}````