Add gitlab CI config and script to pull Travis builds state and result

As long as !60 (closed) isn't solved, which won't happen in the near future I guess, we're using Travis. For convenience, and to prevent merges of branches which are broken (this happened two days ago for example), this MR adds a gitlab CI config and a (python) script to pull the Travis builds state and result. Right now this is a proof of concept, which I've tested with some (known broken) commits. So far this works as expected, but it's quite possible that there are some bugs still to be found. I wrote this in python, because I'm much more faster using this instead of ruby, but this could be changed in the future as well, of course.

Closes #253 (closed)

Any opinions, feedback?