Previously the acceptance test was implemented under the `spec` directory and
was moved out to a top level `acceptance` directory.
This broke the expected location for the node configuration files.
This commit puts the acceptance test back where it was previously.
Also fixes a failure in the test now that Markdown is the default markup
language used.
The specs test functions written in the Puppet language in a few places, but
this feature is only supported in Puppet 4.1+. This commit prevents these
specs from running if targeting older versions of Puppet.