Graphql Kafka Subscriptions Versions Save

• Providing the publish method matching the actual PubSubEngine interface (#24 )
• Simplifying the event channel code using event emitter (#24 )
• Support for message headers and custom message key function (#24 )
• Integration tests with Docker (#24 )
• Improving error handling (#24 )

Thanks to @fmannhardt for great contribution

• Added globalConfig object that get's passed directly to Producer and Consumer
• Updated node-rdkafka
• Updated documentation