This reduces the size of the Docker image from ca. 1.2GB down to about
750MB.
Also, move unit tests from .travis.yml to Dockerfile. Final production
image is not able to run unit tests anymore, as sources are missing from
there.
- Added git version to published labels.
- Minor formatting fix in job template.
- Added .travis.yml and added build status image link to README.
- Added .gitignore.