Revert "Revert "(maint) Replace rspec >= 2.11 expect(foo).to with foo.should""

This reverts commit b4097871e84d7a7b3441130289c594aee859af74.
Merge branch 'maint-rspec_2.9_expectations'

This ensures that GH-423 uses 2.9 expectations since jenkins.puppetlabs.com
uses that version of rspec for testing.