Make exchange name configurable for tap_into listener.
The messages can only be heard from the freddy-topic exchange.
This commit makes the it possible to listen to messages from different exchange
by defining exchange_name option's parameter.'
Make delivery timestamp available for tap into the consumer.
The timestamp is necessary for some applications that need an event start time.
It defaults to nil if the message timestamp doesn't exit.
Make exchange name configurable for tap_into listener.
Make delivery timestamp available for tap into the consumer.