spec_helper: implement an easy way for specs to confine to puppet version

Usage:

    describe 'puppet3 behaviour', :unless => RSpec.configuration.puppet_future do
    describe 'puppet4 behaviour', :if => RSpec.configuration.puppet_future do

Author: DavidS

spec/spec_helper.rb

@@ -23,6 +23,10 @@ module PuppetSpec
 RSpec::Mocks::Syntax.enable_expect(RSpec::Puppet::ManifestMatchers)
 
 RSpec.configure do |config|
+  config.add_setting :puppet_future
+  #config.puppet_future = (ENV['FUTURE_PARSER'] == 'yes' or Puppet.version.to_f >= 4.0)
+  config.puppet_future = Puppet.version.to_f >= 4.0
+
   config.before :each do
     # Ensure that we don't accidentally cache facts and environment between
     # test cases.  This requires each example group to explicitly load the