IPv6 CIDR contains() returns true when it should return false

Here’s an example:

```javascript
ip.cidrSubnet('2001:db8:f53b::/48').contains('2001:db8:f53a::1');
// returns: true, should return false

ip.cidrSubnet('2001:db8:f53b::/128').contains('2001:db8:f53a::1');
// returns: true, should return false
```

This seems obvious so, probably I’m using the library incorrectly, but I can’t see how to fix it.

Start by tracing the cidrSubnet().contains() implementation for IPv6 input and compare its behavior with the two examples in the issue. Add regression coverage for both the /48 and /128 cases, and consider the issue done when each returns false for the address shown.

Written by the indexing model from the issue text.