removed 3D functions from Cython impl
removed 3D functions from Cython impl

instead, we'll just reshape 3D inputs and use only 2D functions. We'll implement
loop tiling in the pure C impl, but it's not worth it to mess with Cython any further.

TadLeonard/husl-numpy,TadLeonard/husl-numpy,TadLeonard/husl-numpy