PHPUnit Updates

Summary: This updates phpunit-selenium from 1.3.3 to 1.4.1, phpunit from 4.2.0 to 4.2.2, and instantiator from 1.1.1 to 1.1.2.
Closes https://github.com/facebook/hhvm/pull/3549

Reviewed By: @fredemmott

Differential Revision: D1511365