Splitted functions in private and public parts

Hi,

I've splitted the code into private and public parts, beside that I've added it to bower and fixed some issues I encountered while I was running the unit tests.

There is one thing I couldn't fix so far, I think that has changed since a Sass update?

The to-string function should cast a color to a string
  ✗ Expected "#000" to equal "black"
  ✗ Expected "#000000" to equal "black"
  Test failed