Fix typo
Update docstrings
Ignore top leve debug modules
Use method_t in exceptions.py

I had to copy over method_t (importing caused a strange error, need to
investigate this).
Add temporary print statements for debugging
Fix incorrect method_id for Exchange.unbind_ok
Add comments
Rename method name strings according to spec

They are lowercase and dash (-) instead of underscores (_) in the spec document.
Add comments
Unify callbacks to accept a single `Method` parameter