Add class matcher that uses a SAT solver to solve the equality constraint solver.
Fix error in pytd.
Add support for some forms of pytd.Generics to the matcher.
Fix handling of missing signatures in incomplete types.
Turn on transitivity to prune invalid solutions (this is reasonable now that I fixed the transitivity constraint generator code).
Change matcher to generate types not classes as the match results.
Improve SatProblem utility class.
Fix bug in visitors.py that put a list inside a hashable data structure.
Improve build structure.
Fix error handling issue left from last CL.
Add experimental SAT encoder for subtype constraint solving.
Implement simple self binding in constraint types by stripping self parameter.
Fix multiple small bugs in constraint types.py.
Add support for setting initial polarity to SATProblem.
(Also sneak in Moe db update)
Fix Python 3 compatibility. See https://github.com/google/pytypedecl/pull/2
Add syntax for conditional compilation (based on Python version.)