Merging topic/python into master

Dear all (cc @olivier-stasse ),
it appears that topic/python and master have diverged quite a lot.

Would it be possible to:
1. rebase topic/python on top of master
2. merge the branch?

AFAIK no one is using master so it should not impact anyone.

Another good side effect would be that we could check this package on travis now that the hrp2 dependencies are optional.