Add support for IP Address Ranges

I had been thinking on trying to add this feature myself (and maybe I'll still try and get around to it), but I've been busy. So I thought I would open an issue in case someone else can get around to adding it before I do.

Add support for pinging a range of IP Addresses, similar to how it works in nmap.

something like gping 192.168.1.10-15 instead of having to type out gping 192.168.1.10 192.168.1.11 192.168.1.12 192.168.1.13 192.168.1.14 192.168.1.15