Add hiera validation to CI definitions.

[JacobHenner]

To compliment puppetlabs/pdk#246 and puppetlabs/pdk#424, the default pdk template should include steps in each CI definition for validating/linting module-scoped hiera data. yaml should definitely be supported, and perhaps json too?

[DavidS]

This is being tracked in https://tickets.puppetlabs.com/browse/PDK-742

[scotje]

This issue was moved to puppetlabs/pdk-planning#24