Returning tests for backward compatibility.
Fixing typos.
Reimplementing old family and parent_family methods.
Bugfix: family accidentaly calls itself.
Implementing siblings method.
Reimplementing common ancestors.
Renaming and fixing method finding mutual parent families.
Reorganizing and optimizing tests.
Fixing common ancestors in path finding.
Fixing common_ancestor_families - parent is not ancestor of himself.
Fixing incorrect tests.