(maint) Add temp workaround for travis

Rubygems broke travis builds on ruby 1.8.7:

https://github.com/travis-ci/travis-ci/issues/1793
https://github.com/rubygems/rubygems/pull/763

This patch is a temporary workaround until rubygems is
updated.
Merge branch 'master' of https://github.com/puppetlabs/puppet