Updated Readme as CakePHP Shell Scripts is now on Packagist

https://packagist.org/packages/loadsys/cakephp-shell-scripts
Signed-off-by: Justin Yost <justin.yost@yostivanich.com>
Updated Readme to reflect this is published on Packagist

Signed-off-by: Justin Yost <justin.yost@yostivanich.com>
Merge pull request #2 from jtyost2/f/packagist-installable

Updated Readme as CakePHP Shell Scripts is now on Packagist