Use a pipeline to publish and consume messages

[jessehansen]

This replaces the old publish and consumption methods with a more generic pipe/filter pattern, implemented using magicpipes.

[jessehansen]

Goals before merge/release:

• 100% test coverage for amqp folder
• 100% test coverage for state machines
• 100% test coverage for everything else
• Add broker.host #3
• Support multiple message types #8
• Make envelope usage and serialization part of a generic pipeline (decorator pattern) #11
• Support creating exchange at publish time #12
• documentation

[coveralls]

Coverage increased (+6.08%) to 86.912% when pulling d1a8b53 on pipeline into 083451f on master.