Add note about publicly consumable types
Add note about publicly consumable types

Add a note to the docs that describes that these are
made for public usage; and that even so they still may
be moved to new supported libraries at various points
in the future.

Change-Id: I172531ee07878eb5ef46821a5f3dc2fc3ce8c439

pombredanne/taskflow-1,openstack/taskflow,junneyang/taskflow,jimbobhickville/taskflow,pombredanne/taskflow-1,openstack/taskflow,junneyang/taskflow,jimbobhickville/taskflow