This work updates a number of Gems to the latest versions (rspec,
rspec-puppet), and updates and tweaks a bunch of tests to work
with the updated gems.
This updates the Rakefile and spec_helper to use the common versions
available in the puppetlabs_spec_helper rubygem branch. This mostly
just removes a bunch of duplicated code, but it also gives us more
flexibility in how the module is tested in the future.
