starting total overhaul of affine expressions
migrating affine operators to atoms
made AffExpression a subclass of expression
working on vstack and atoms
changing coefficients calculation to use numpy ndarrays
removed bool mat in favor of sparse bool mat
cleaning up and adding docstrings
finished rewrite of utilities
added bool ndarray's back in to speed things up
Added coefficients class, now need unit tests
Added coefficients utility
added coefficients unit test
passes all unit tests. needs speed up.
separated canonicalization from param evaluation and fixed build
fixed travis and cached canonicalization
separated out constant atoms and cached coefficients
cleaned up constant atom
separated variables and parameters methods from coefficients and cached coeffs with no params
added ordered set from recipe and uniquefied constraints
boosted speed by changing add atom to be more like sum