Configure and enable Travis CI configuration for hhvm unit tests

Adds hhvm to travis unit tests with failures allows.

Modifies invocation of phpcs and phpunit to use vendor supplied
copies[via composer] needed for hhvm to function.

Removes PEAR/PYRUS installs of phpcs and phpunit in favor of composer
installs.

Conflicts:
	composer.json

Signed-off-by: Gary A. Mort <garyamort@gmail.com>