Add support for RabbitMQ through amqplib

**Is your feature request related to a problem? Please describe.**

`apm-agent-nodejs` supports databases and Redis but not AMQP-related messaging services like RabbitMQ.

**Describe the solution you'd like**

Add a wrapper for `amqplib` which will:
- open a span when a message is sent
- open a transaction when a message is received

**Describe alternatives you've considered**

**Additional context**