Return absolute (fully-qualified) name for nodes
Add type hints
Add helper to get all sub-tasks
Unify getting (resolving) single tasks
Return all task nodes (including groups)
Return all tasks in task listing

Task listing should be irrespective of whether tasks have a
description assigned
Add Node::is_visible() logic and additional helpers
Merge branch 'master' into all-tasks

Conflicts:
	lib/phake/Builder.php
	lib/phake/Node.php
	lib/phake/Task.php
Merge pull request #25 from clue/all-tasks

Return all tasks in task listing