Update README to include Composer info
Update README to include Composer info

Includes instructions for updating composer and for installing CakePHP when Composer is installed globally.
ojengwa/cake-appengine,ojengwa/cake-appengine,makallio85/fish-diary,QoboLtd/project-template-cakephp,makallio85/fish-diary,QoboLtd/project-template-cakephp,QoboLtd/project-template-cakephp,makallio85/fish-diary,QoboLtd/project-template-cakephp,QoboLtd/project-template-cakephp