Implement CI and CD

[vbrandl]

Once #2 is done, it should make sense to implement CI and CD for this service. Maybe there should also be a staging environment for the HEAD on master and only tagged commits get deployed on prod.

[vbrandl]

CI is implemented and works. Currently the project is build on travis, gitlab CI and drone.vbrandl.net.

To prolong the heat death of the universe, at least one of the services can be dropped.

No idea yet on how to implement CD.