[spec] fix puppet-rspec regexp (refs: #126)

According Andrew comment on
https://github.com/sbadia/puppet-gitlab/pull/126#issuecomment-37826055
our regexp can match not wanted things… this commit fix this problem.

Thanks Andrew!
Merge pull request #129 from sbadia/feature/126/better-matchs

[spec] fix puppet-rspec regexp (refs: #126)