Add SchemeT type
Add SchemeException
Add MonadThrow type class to SchemeT
Use SchemeT
Add resourcet package to build-depends of the test-suite section
Use (ProperList | DottedList) instead of Pair
Use ProperList and DottedList in tests
Flatten dotted list
Don't use state monad
Use IORef in Env type
Unify proper list and dotted list
Add function type
Add EnvRef to eval
Add define
Add apply
Relax type signature
Add primitive function