An optimization in the computation of the simplex's volume, some minor refactoring and naming fixes.
Implement the calculation of the volume of a 3d simplex in C for performance, and revert to assigning a volume of -1 to protruding cells.
Compute the neighbours list directly as a numpy array and start using the multiprocessing utils.
Rewrite more functions in C and parallelize the computation of volumes and bbs.
Minor cleanups and commenting.
Run autopep8 on voronoi_helpers.py.
Fix spelling errors in comment.
Clean up some debug statements and add optional support for pinning the processes to a processor.

The latter greatly enhances performance stability on hyperthreaded machines.
Merge pull request #3 from bluescarni/voronoi_take_3

Voronoi take 3