Fix phpunit version to 3.7.31, 4.X version has phpunit-mock-objects issues
Fix phpunit version to 3.7.31, 4.X version has phpunit-mock-objects issues

sproogen/php-saml,dialogik/php-saml,samlev/php-saml,davidjnelson/php-saml,stayallive/php-saml,Ricky-rick/php-saml,onelogin/php-saml,mzbac/php-saml