a tidy of some 4D interpolation code ( remove unnecessary blend2 variable )
Value2D_Deriv, Value3D_Deriv and Perlin3D_Deriv added
SimplexPerlin2D_Deriv and SimplexPerlin3D_Deriv added
Cellular2D_Deriv and Cellular3D_Deriv added
Initial Wombat description added to ReadMe file