(Maint) Add spec/functions to rake test task

Without this patch the `test` rake task does not exercise the
rspec-puppet behaviors located in spec/functions/  This is a
self-evident problem.

This patch fixes the problem by adding spec/functions to the list of
directories scanned for spec tests.

Rakefile

@@ -5,7 +5,7 @@ task :default => [:test]
 
 desc 'Run RSpec'
 RSpec::Core::RakeTask.new(:test) do |t|
-  t.pattern = 'spec/{unit}/**/*.rb'
+  t.pattern = 'spec/{unit,functions}/**/*.rb'
   t.rspec_opts = ['--color']
 end