clean up travis.yml

[e-hein]

[warn] on jobs.include.deploy: deprecated key: "skip_cleanup" (not supported in dpl v2, use cleanup)

[warn] on jobs.include.deploy: deprecated key: "skip_cleanup" (not supported in dpl v2, use cleanup)

[info] on jobs.include.deploy: the key api_key is an alias for token, using token

[info] on jobs.include.deploy: the key api_key is an alias for token, using token

[info] on jobs.include: duplicate values: name: Update preview