fix hiera documentation in relation to deep_merge_options in hiera.yaml

:deep_merge_options: needs a ruby hash, not a yaml hash
https://docs.puppetlabs.com/hiera/3.0/configuring.html#deepmergeoptions

original, as per docs was:

:deep_merge_options:

  :merge_hash_arrays => true

new, and now working with hiera_hash:

:deep_merge_options: {

  merge_hash_arrays => true

}

we could either doc this, or do an internal conversion of yaml to ruby datatypes I think.