First feature release

Features

operator_registry: meta field to event

New optional meta field is introduced to the event structure in order
to serve future purposes on so called meta-requests serving
information about the OperationRegistry and the registered operations.

operation_registry: doc option is added to meta

The meta field serves a purpose to hold control information for
ratatoskr about the event.
The newly introduced doc field is a Boolean type that controls if the
requestor of the event wants to get back the docstring of the registered
operation.
The base wrapper introduced a new class method help(cls) that returns
the docstring of the function. It can be reimplemented in derived
classes if the developer has intention to serve this documentation from
another source.

Enhancements and fixes

schema: remove args from required fields

args field is not required anymore. operation field is the only
required payload for an event.

setup.py: pip req versioning fix

Pip 10 is changed module structure with pip.req. Adding proper import
handling logic to the setup.py to install properly.