Test against more recent versions of stdlib

[ubellavance]

This module only supports stdlib <5, while the most recent version is 5.1.0. I did simple testing by using all the hiera examples in the Readme.md and it worked OK. RHEL 7.

If we install the most recent version of stdlib, then install this module, it installs version 1.2.2, because at that time the requirement was stdlib >= 4.2.0

[ebdavison]

I am using puppet 6.0 and cannot use the most recent version 3.4.0, since it relies on stdlib < 5. The newest version supported on puppet 6.0, from what I can tell, is 1.2.2 and this is VERY old.
Please update as stated above to current version of stdlib as stated above so that this will work with current version of puppet.