Build and push the Docker images on `master`

[sroze]

All we need to do is to run the following commands (with the correct docker login before) in Travis:

docker-compose -f docker-compose.yml -f docker-compose.images.yml build
docker-compose -f docker-compose.yml -f docker-compose.images.yml push

[Simperfit]

Do we have the credentials in the repository ?

[sroze]

Nop, but we could set it up on Travis