v0.2.7 release

Full Changelog: 0.2.6...0.2.7

• Improve the python interface with easier access to the underlying objects:
  • path.get_node() -> path.node
  • path.get_group() -> path.group
  • path.add_node(node, label) -> path[label] = node
  • path.show_tree(decroate_function) -> path.show_tree(decorated_by=['label', 'uuid_first_12']