Add note about where to add plugin test suites.
Add note about where to add plugin test suites.

makallio85/fish-diary,QoboLtd/project-template-cakephp,QoboLtd/project-template-cakephp,ojengwa/cake-appengine,makallio85/fish-diary,QoboLtd/project-template-cakephp,makallio85/fish-diary,QoboLtd/project-template-cakephp,QoboLtd/project-template-cakephp,ojengwa/cake-appengine