add Google's algorithm

[filipeglfw]

Added two new algorithms:

Google

This will reproduce exactly what Google's color tool generates. Sometimes this tool slightly changes the input color. For exemple, when inputing #350094 it will return a pallete with #340094

Google exact

I am terrible at naming things, so you're welcome to change this. I've tweaked the code from the previous algorithm so that it will return the input value exactly.

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Google's original Material Palletes did not have A colors for the Brown, Gray and Blue Gray, so that the algorithm will not return A colors in case the input is close to those.

Closes #118

[filipeglfw]

Just as a reference, here are the palletes generated with the algorithm compared to the one from Google's documentation.

[SimonIT]

@mbitson