Bump docker to 1.12.6, docker-compose to 1.9.0
Bump docker to 1.12.6, docker-compose to 1.9.0

ljharb/travis-cookbooks,spurti-chopra/travis-cookbooks,travis-ci/travis-cookbooks,ljharb/travis-cookbooks,ljharb/travis-cookbooks,spurti-chopra/travis-cookbooks,spurti-chopra/travis-cookbooks,travis-ci/travis-cookbooks,travis-ci/travis-cookbooks