Add beaker acceptance tests

Very basic beaker tests.  Adding other operating systems and operating system releases should only require adding new node definitions under `spec/acceptance/nodesets` and appropriate files under `spec/acceptance/support`.  May be useful to begin system based tested of future changes.

The file content checking isn't great, as I had issues making multiline strings work using:
```ruby
its(:content) { should match expected_content }
```

Some of the file contents worked, some didn't.  Likely due to characters that break the matchers used in serverspec.