Added choice(...) syntax.
Tests and sanity checks for choice().
Added pyll converter + tests.
Remove dead code, simplify.
Make Literals more lightweight.
Conditional test execution for pyll.
Better ImportError message.
pyll free variable conversion.
Better handling of short circuits.
Move sequence special-casing inside _convert_partialplus.
Catching repeats unnecessary with toposort.
Non-categorical variable converters.
Uniform categorical support.
Get rid of unnecessary assignments.
Miscellaneous cleanup.
Choice node support.
Test repeated node gets converted identically.
Support for non-uniform categoricals.