cidrSubnet() is skipping first/last address

AFAIK, `ip.cidrSubnet('192.168.1.0/30')` should return 4 hosts in the range `192.168.1.0 - 192.168.1.3`, but it actually returns 2 hosts in the range `192.168.1.1 - 192.168.1.2`.

I checked out the source code and the reason is pretty obvious in `subnet()`:

```
firstAddress: numberOfAddresses <= 2 ?
ip.fromLong(networkAddress) :
ip.fromLong(networkAddress + 1),
```

However, I can't understand the reason of such implementation. What am I missing?

Thank you,
Marco

Start at the `subnet()` implementation reached by `ip.cidrSubnet()` and reproduce the `192.168.1.0/30` example from the issue. Determine whether excluding the first and last addresses is intentional, then make the returned count and range match the agreed behavior and add regression coverage if the repository has a suitable test entry point.

Written by the indexing model from the issue text.