make python style default

There is no need for a python style since all code is now Python.
The python style was leftover from the days we had two versions of the
lab manuals.
Merge pull request #238 from ayr0/styles

make python style default
add new material to vectorization lab

Add more discussion and a figure to vectorization lab.
Merge pull request #239 from ayr0/vectorlab

add new material to vectorization lab
Changed an error in the description of the helper function for the Voronoi
lab.
Added a little to the description of the second problem in the voronoi
lab.
Merge pull request #242 from insertinterestingnamehere/voronoi

Voronoi