Added leading slash to closure to prevent reference to PHPCI namespace

Don't forget to put \ in front of PHP namespaced objects or you end up in your own namespace.

In reference to commit: https://github.com/Block8/PHPCI/commit/53993a1add01e2945ae64de787b0634f0c0a10e9
Merge pull request #171 from crazycodr/patch-1

Added leading slash to closure to prevent reference to PHPCI namespace