Update manifest spec tests for Puppet 4
Update manifest spec tests for Puppet 4

Now that Puppet 4 is released, tests can accurately be written to
confirm the behavior of syntax testing. While the actual project runs
just fine against Puppet 4 by hand, the tests currently fail.

This commit updates the unit tests written against the
`PuppetSyntax::Manifests` class to confirm that the previously available
behaviors are still functioning correctly on Puppet 4. The refactored
tests stop running some of the future parser related tests on Puppet 4,
but still add a test to confirm everything works fine. With this commit,
this project should start passing correctly when tested against Puppet 4.

gds-operations/puppet-syntax,gds-operations/puppet-syntax