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.
add /sbin to Exec path
This caused the unless expression to fail for 'ufw-default-deny' in
Ubuntu 14.04, resulting in an exec on every puppet run.

This patch fixes issue #28
Merge pull request #29 from deedoubledub/master

closes #28 Add /sbin to Exec path
closes #20 Adding documentation on adding ranges
updating travis instructions
Remove trailing s per #27
Merge pull request #27 from andschwa/hiera

Using hiera_hash to allow for merging of hashes
Update Modulefile