sorry, meaningless commit
Introduce Reader Monad.

Reader Monad is introduced to convert ( = nfa2dfa . enfa2nfa). An epsilon NFA at enfa2nfa and a NFA at nfa2dfa is never changed, so they are implicitly passed. These changes passed tests, but probably need refactoring.
Change the data structure of NFATrans.

NFATrans was Map StateNumber (Map (Maybe Char) [StateNumber]), but is Map StateNumber (Map (Maybe Char) StateSubset) now. Become more intuitive.
Complete refactoring and comment.