chore(Travis): use lowest possible packages for PHP 5.4
chore(Travis): use lowest possible packages for PHP 5.4

sphereio/sphere-php-sdk,sphereio/commercetools-php-sdk,sphereio/commercetools-php-sdk,sphereio/sphere-php-sdk,sphereio/commercetools-php-sdk,sphereio/sphere-php-sdk,sphereio/sphere-php-sdk,sphereio/commercetools-php-sdk