ci: Add travis.yml and run GoReleaser on tags

[markus-wa]

This adds a Travis CI config that runs GoReleaser on tags.

Example Build: https://travis-ci.org/markus-wa/ifacemaker/jobs/462909911

Generated Release: https://github.com/markus-wa/ifacemaker/releases/tag/v0.1.0

What needs to be done from your end for this to work:

• Configure Travis: https://travis-ci.com/getting_started
• Configure GITHUB_TOKEN environment variable in Travis: https://docs.travis-ci.com/user/deployment/pages/#setting-the-github-token
• Create a first tag (I'd suggest v0.1.0 to not be too concerned with backwards compatibility for a start)
• Maybe more, it feels like there's something missing :sweat_smile: