make the guide run out of the box again with an embedded broker as shown
in the readme. this should fix the issues #8 and likely #6, too.
Merge pull request #9 from zyro23/issues-6-8

Due to https://github.com/spring-projects/spring-boot/commit/c4ffe721c786c54074a6913cb889d46e83bb32c1, *pubSubDomain* was switched from true to false as the default. Hence, the SimpleMessageListenerContainer has to change as well, as shown in this PR.