Fix root domain name parsing

[silverwind]

This fixes a query for the root zone (issued from native-dns), like this:

var question = dns.Question({
    name: "",
    type: "NS",
});

Previously, the returning packet to this query could not be parsed and native-dns never received the packet and ran into a timeout.

From RFC 1035: The root domain name is defined by a single octet of zeros at 92; the root domain name has no labels.

[silverwind]

One part I wasn't totally sure was if the buffer cursor should be seeked forward by one byte before running buff.tell() to return the current location. The results seem fine with my current method though.

@tjfontaine any thought on this part?

[sindresorhus]

👍 You should probably add a test ;)

[silverwind]

I'll look into adding a test.

[taoeffect]

@silverwind #7 was just merged. Could you check to see if this is relevant to that? (I'm focusing on releasing update to native-dns based on #7, which included many changes/fixes). If it is, can you submit the PR on top of most recent master?

[silverwind]

@taoeffect I think it should still apply, I'll rebase my branch shortly and test if everything is working fine.

Regarding the tests: I think there were 2 tests failing in the current build, and from a first glance, I think I need to tinker with the testing methods for it to test a "" lookup correctly. Will let you know how that turns out.

[taoeffect]

Thanks @silverwind! Feel free to add your name to package.json in the list of authors! :)

[silverwind]

Will do, will probably check this out tomorrow.

[silverwind]

Looks like this PR is obsolete with your change in #7 which added end = buff.tell();. Queries for empty strings now work as expected. Great work!

[taoeffect]

Awesome (thx)!