A utility to assist in splitting a subnet into smaller subnets.
Currently only supports IPv4, which IPv6 hot on it's tail.
$> subnet_split "172.16.0.0/24" 30
172.16.0.0 30 172.16.0.0/30
172.16.0.4 30 172.16.0.4/30
172.16.0.8 30 172.16.0.8/30
...