internal-ip

See https://github.com/silverwind/default-gateway/issues/27. I intend to deprecate it soon because I just don't feel like maintaining these calls any more. This module should go back to being a simple parser of like linked here.

The module currently assumes that the default gateway lies within one of the configured interface subnets but there are cases where this assumption does not hold true. One example is a Travis VM having with gateway . Strictly speaking, this is a invalid network configuration but it somehow still works so we need to account for it. One approach could be to find the address nearest to the gateway. It's a guess but chances are it might be correct. To get the nearest IPv6 adress conveniently, we need to convert both the address CIDR and gateway address to a BigInt and then compare them, so I would like to require native BigInt (node 10.4.0+).

This PR is an attempt to fix #48. I would like to add some tests, but this would require mocking a bunch of dependencies. Is this possible with ESM and Ava?