Function parse_addresses 

pub fn parse_addresses(input: &Opts) -> Vec<IpAddr>

Parses the string(s) into IP addresses.

Goes through all possible IP inputs (files or via argparsing).

let mut opts = Opts::default();
opts.addresses = vec!["192.168.0.0/30".to_owned()];

let ips = parse_addresses(&opts);

Finally, any duplicates are removed to avoid excessive scans.