Automatic building

[bountin]

After upstream package updates happen these images should be rebuild to contain the newest (and most secure) versions.

Alternatively a daily build would work too.

Build system can be at 25th-floor inhouse, or maybe TravisCI is also a good solution.

[bountin]

The official dockerhub supports building but no testing. TravisCI on the other hand can be completely configured which allows tests of built images and maybe even generation of the Dockerfiles itself.