Update Module Documentation

[Bradley Dice]

Modules lacking documentation:

• shapesplit, see #78 (removing shapesplit is an alternative)

Other documentation needs:

• Explicitly describe memory management approach, see #152

[Bradley Dice]

In progress.

[Bradley Dice]

Updates: I added documentation for voronoi and parallel. I fixed the box, pmft, kspace docs.

[Bradley Dice]

Consolidated remaining tasks into other issues #78 and #152.