Implementation of Perlin noise.

Example of use:

main = putStrLn ("Noise value at (1, 2, 3): " ++ show x)
    where seed        = 1
          octaves     = 5
          scale       = 0.05
          persistance = 0.5
          perlinNoise = perlin seed octaves scale persistance
          x           = noiseValue perlinNoise (1, 2, 3)