Make hook runner Ruby 1.8 compatible

Although in general it's not a good assumption that your code needs to
be loaded via rubygems (being agnostic to installation methods), there's
a necessary evil here.

Change-Id: Ie45db8001321d7c8522dac5e3d39e6bc2ece1342
Reviewed-on: https://gerrit.causes.com/22768
Tested-by: Aiden Scandella <aiden@causes.com>
Reviewed-by: Aiden Scandella <aiden@causes.com>