update travis.yml

[k-okada]

Created travis.yml using

• https://github.com/ros-infrastructure/ros_buildfarm/blob/master/doc/jobs/devel_jobs.rst
• https://github.com/ros-infrastructure/ros_buildfarm/blob/master/doc/jobs/prerelease_jobs.rst

Please activate GitHub - TravisCI integration to enable this test https://github.com/apps/travis-ci

[k-okada]

travis is not enabled on this repo, I have confirmed it is compilable on ubuntu:focal