Add v0.0.6 optimizations back in once we've figured out what the bug was

[emilydolson]

v0.0.6 breaks some really simple proofs-of-concept in https://github.com/emilydolson/lex-prob-is-np-hard, so there is definitely something wrong with it. Need to figure out what it is, add tests that catch it, and add a fixed version of the optimizations back in.