docker-compose: Send Trillian logging to stderr
docker-compose: Send Trillian logging to stderr

Makes it easier to see logging when Trillian is running inside Docker
containers.

daviddrysdale/trillian,gdbelvin/trillian,Martin2112/trillian,Martin2112/trillian,AlCutter/trillian,daviddrysdale/trillian,gdbelvin/trillian,RJPercival/trillian,gdbelvin/trillian,daviddrysdale/trillian,google/trillian,Martin2112/trillian,AlCutter/trillian,RJPercival/trillian,google/trillian