Implemented a publish call in listener DSL

The publish call can be used to publish a new message
from the listener to other micro-services.
A block can be passed as a callback for the response.

Also did some refactoring to allow this change.

Note: AMQP subscriber tests have two failures as of this commit.

	modified:   gilmour/backends/amqp.rb
	modified:   gilmour/backends/backend.rb
	modified:   gilmour/backends/redis.rb
	modified:   gilmour/responder.rb
	modified:   ../test/spec/test_subscriber_redis.rb
	modified:   ../test/testservice/subscribers/test_subscriber.rb
Bump gem to v0.0.5