Handling a floating point issue

Try calling 
```
[1] pry(main)> a = Paleta::Color.new(:hex, '00736D')
[2] pry(main)> a.lighten(20)
```
Running on JRuby 1.7.16 it will throw an `ArgumentError, "Component range exceeded"`

Started using dup instead of a complete initialization to save that and to simplify matters. Then also added a test for the issue generating this. it would get a saturation of **100.00000000000003** because of all the unneeded math.