This work follows Stefan Gustavson's paper "Simplex noise demystified"
http://www.itn.liu.se/~stegu/simplexnoise/simplexnoise.pdf
without using uniform arrays or texture engines.

The resulting noise functions are fast and self contained,
and their performance scales well with massive parallelism.

Simplex noise functions are (C) Ashima Arts
Classic noise functions are (C) Stefan Gustavson

Source code for the noise functions is released under the
conditions of the MIT license. See the file LICENSE for details.