(maint) Remove warning about expect().to in specs

The Puppet Gemfile is pinned against RSpec 2.11.x, so there should be any
reason to worry about RSpec 2.9.x.
Merge pull request #2775 from Sharpie/remove-rspec-29-warning

(maint) Remove warning about expect().to in specs
Merge branch 'master' of https://github.com/puppetlabs/puppet