requirements fix

git-svn-id: https://silverstripe-ecommerce.googlecode.com/svn/modules/payment_dps/trunk@4806 950b781c-c544-efab-2f99-90083ee69683
UPGRADE 3.1

git-svn-id: https://silverstripe-ecommerce.googlecode.com/svn/modules/payment_dps/trunk@4813 950b781c-c544-efab-2f99-90083ee69683