OVERVIEW:

A toy BDD implementation in python, based on Knuth's AoCP, Vol 4 Fascicle 1

TODO:

0.  add an early-termination check for partitions that are connected (ie partition contains only one subset that is the whole set of vertices) - this might save a little bit of computation toward the end of the tree.

1. add script to generate Knuth-style BDD diagrams with graphviz
	impose ordering (variable tested must decrease)
	use dashed and solid for low, high branches
	use circles for branches and squares for sinks

2. implement algorithm R to reduce the horrific tree things connection.py generates