Add source of engine-state sequence diagram
Add source of engine-state sequence diagram

To allow others to recreate this sequence diagram
include the source to that diagram so that it can
be regenerated (if needed) in the future.

Change-Id: I68dfea274e679e09a9d5e34af28d05d766856686

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