title: RabbitMQ-- selectively retrieving messages from a queue
body: <p>I'm new to RabbitMQ and was wondering of a good approach to this problem I'm mulling over.  I want to create a service that subscribes to a queue and only pulls messages that meet a specific criteria; for instance, if a specific subject header is in the message.</p>
  
  <p>I'm still learning about RabbitMQ, and was looking for tips on how to approach this.  My questions include: how can the consumer pull only specific messages from the queue?  How can the producer set a subject header in the message (if that's even the right term?)</p>