0.4.0

• Support for Encoders/Decoders of different message types.
  This is a breaking change that enforces update of client code to explicitly decalare a proper Decoder/Encoder instead of using raw Strings. In case you want to keep String-based messages, use a new StringEncoder() or new StringDecoder(). Thanks @javierarrieta for this contrbution! (#7)
• Fixed the consumer behavior when new messages appear in stream.
  When connected to a Kafka queue, the flow was consuming all the present elements but after that, new elements were not polled correctly. This fix assures that an ActorPublisher keeps polling Kafka for new elements if there is demand.