add support to verify sudoers

Hello, this module now merges all the sudoers entries specified in hiera in /tmp, runs "visudo -f <path_to_merge_file> -c" and  then if all is good pushes the new sudoers out to /etc/sudoers.d/

Spec tests went well so nothing was destoyed.. (famous last words), but writing new spec tests for my change might be a bit tricky.