Classfiy custom types and add EnumType to it.
Stylistic adjustment and add missed __all__.
Fix type error and add test on sqltypes.py.
Add name to EnumType in test since pgsql needs it.
schema-level adjustment for PostgreSQL Enum.
Merge pull request #17 from sjw0687/types

Classfiy custom types and add EnumType to it.
Handle network error