Use hiera_hash(...) instead of hiera(...) so that matches throughout the Hiera hierarchy can be merged.

See https://docs.puppetlabs.com/references/latest/function.html#hierahash
Merge branch 'master' of https://github.com/michaelmoussa/puphpet into michaelmoussa-master
Revert "Use hiera_hash(...) instead of hiera(...) so that matches throughout the Hiera hierarchy can be merged."

This reverts commit 833a1664829c64141016b7c6e483335844043fbf.
Replaces all instances of hiera() with hiera_hash(). Closes #977