Initialize certain methods in context.py and added __init__.py

Looks like zerorpc-python doesn't even run without initializing the following methods in context.py:

_middlewares, _msg_id_base, _msg_id_counter, _msg_id_counter_stop

This is somewhat of a hotfix and not a permanent solution, but it got zerorpc-python up and running.
Major bug fix, init @properties in context.py
Added __init__ to make a py module