Automatic tests for docker-compose

[nupplaphil]

As already said in a PR, I want to increase the automatic testing.

So I do want to add Travis CI tests for all of the docker-compose examples. Like we have for the dockerfiles examples.

Therefore I have to download and execute the docker-compose binary on-the-fly during the Travis runs :-)

[MrPetovan]

I don't understand everything but I'm with you.