Fix issue with IpAddress where to_s only return the ip address, and we need to_string

[fr3nch13]

For IP Addresses, we need to do the comparison using to_string instead of to_s so we also get the cidr.

https://github.com/ipaddress-gem/ipaddress/blob/064502c6a943f983cabea38fccdb528ad9469aec/lib/ipaddress/ipv4.rb#L179

[fr3nch13]

I'll open a PR for this in a minute.