Merge branch 'groups_vs_group' into 'master'
Fixes #33 I am now checking that the ``--group`` and according options are not used w/o ``--sub-task``. A test case is yet missing, but will follow soon. Note that I will need to modify ``bob.bio.gmm`` accordingly, unless someone finds a better and more generic solution to #33 Accepting this merge will close #33. See merge request !34