ValueError at high Octaves & Lacunarity

[AyrtonB]

When using larger octaves and lacunarity (e.g. 2 & 3 respectively) the following error occurs in perlin2d

ValueError: operands could not be broadcast together with shapes (1024,1024,2) (1023,1023,2)

At the line

n00 = np.sum(np.dstack((grid[:,:,0] , grid[:,:,1] )) * g00, 2)

I believe this is because the delta tuple doesnt consider what happens when there's a remainder from shape/resolution

[AyrtonB]

Have added a check for valid resolutions in #7