use phpunit 4.1.x for testing

Signed-off-by: Chirayu Chiripal <chirayu.chiripal@gmail.com>
install composer packages for hhvm also

Signed-off-by: Chirayu Chiripal <chirayu.chiripal@gmail.com>
Merge pull request #1348 from D-storm/travis

use phpunit 4.1.x for testing (Travis)