(GEP-172) Support resource body with arbitrary rvals in title

Puppet versions >= 4.0 will allow using arbitrary rvalue expressions
as the title in resource bodies. This commit ensures that Geppetto
doesn't complain about such expressions unless the target platfrom
is < 4.0.
Use less complicated resource when testing invalid resource title.
Merge pull request #45 from puppetlabs/issue-172

(GEP-172) Support resource body with arbitrary rvals in title