Pass phpunit env vars

Passes along phpstorm's phpunit-related environment variables to enable the non-default usage of a custom-loader to work around the default include-path option which is incompatible with phpunit 4+.

Note: This only helps phpstorm8, as phpstorm7 is incompatible to phpunit4+.

Related issue: http://youtrack.jetbrains.com/issue/WI-22392