'net' module: tests and fixes

So far this updates #308 with a very basic test suite, and fixes IPv4 and/or IPv6 address detection.
Not sure why the relative path is required? That's weird, since I did rebase to master. (And locally is no longer required.)

Here's how many tests I think there are:
`cat test/suite/net.js | grep \\bt\\. | grep -v t\\.end` says 35
The IP format tests loop…`validIPv4.length` is 5, `validIPv6.length` is 14, `totalBunk.length` is 13 — 32 total and each is iterated over 3 times. So 35, minus the 9 verbatim test calls, plus the 96 actual test calls is 122. Two of those are `t.fail` calls that should *not* execute. So 120 is the right number…and perhaps not coincidentally, the number of tests that were running before switching to tinytap.

I will look into the 106 failures next.