Fix syntax error in mutator
Port method extraction to parser based ast
Port mutation generator infrastructure to parser
Do not ugnore underscored symbols in util mutator

This *ignore* should be done at the argument / variable mutator!
Port literal boolean mutator to parser
Port single variable assignment mutator to parser
Fix begin mutator
Fix util array mutator to not modify frozen input
Port define mutator to parser
Port argument mutators to parser
Port literal nil mutator to parser