Fixes incompatibility with RSpec 3.0.0

* Pin rspec dependency to < 3.0.0 Fixes #200
* Fix deprecation warnings related to 'display_name', fixes #198

Same solution as #199 but also pins rspec-puppet to RSpec < 3.0.0 as there are likely numerous other issues people will face when depending on rspec-puppet to pull in the necessary rspec dependencies.