Install Nagios NRPE plugin.

This commit refs #142.
Install check_nrpe in the Nagios server.

This commit fixes #142.
Merge branch 'id/142' into dev
Install nrpe by default when deploying AWS servers.

This commit refs #142.
Merge branch 'id/142' into dev
Merge commit '061a18e558a976802c810280f3df4a82bac31053' into HEAD