Parallel pull for docker-compose

[arcusfelis]

This PR addresses "Travis is slow!".

Proposed changes include:

• use docker pull --parallel
• use "docker-compose tries to resolve an ip, so slow" - not sure, if we actually need it.

[michalwski]

This is quite good idea, on the other hand after quick comparison with old jobs, this change doesn't save much time (around 10-20s). It still may be useful when we have more containers in tests.

[arcusfelis]

true, also sometimes the docker pull can take 3-11 minutes for some reason (travis is slooow?).
In this case parallel pull can be useful.