Scaffolding

Setting up the scaffolding for the project.  Two types of generators:
the dense, standard Saidman one and a TBD heterogeneous (and sparse)
one.  A solver class, just implementing one with raw CPLEX now for the
AAMAS submission.
Updated README.

Included an explanation of kidney exchange, references to some of my
papers, and references to people in the field.  Need to do some sort of
"this is how kidney exchange relates to Econ-CS" formalism writeup
eventually.