Using hiera_hash to allow for merging of hashes

Wish I'd known about this in my prior PR, but this is a better way to
get the values. `hiera_hash` is a built-in function that allows Hiera to
merge hashes in the manner specified in the Hiera configuration file.
Remove trailing s per #27
Merge pull request #27 from andschwa/hiera

Using hiera_hash to allow for merging of hashes