Update docstring

Reformat docstring
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
Fix reference to parameter name in docstring
Use dict param in GenericContent instead of kwargs
Update usages of GenericContent to use `properties` dict
Fix typo in docstring
Rename instance variable

`methods_sent` is a correct name
Rename `Method.channel` to `Method.channel_id`

This is a more appropriate name which reflects the type of the variable.
Rename METHOD_MAP (remove leading underscore)
Pass isinstance a tuple (code clarity)
Clean up code and docstrings