Doesn't respond with SERVFAIL when throwing an error #2

When an error is thrown (such as malformed json data that cannot be written as binary), the server should respond with SERVFAIL

Here's how to observe this error:

Create a db file with bad data (the required field "exchange" is missing from the MX record):

fail.json

{
  "primaryNameservers": [ "localhost" ]
, "domains": [ { "id": "example.com" } ]
, "records": [

    { "zone": "example.com", "name": "example.com", "tld": "com", "sld": "example", "sub": ""
    , "type": "MX", "priority": 10, "MISSING-exchange": "mxa.example.org" }
  ]
}

Installing and running the digd.js server:

git clone https://git.coolaj86.com/coolaj86/digd.js.git

pushd digd.js/

npm install

node bin/digd.js --port 5353 --input fail.json +norecurse

In another terminal, while the server is running:

dig @localhost -p 5353 MX example.com

The server throws an error and nothing comes back. Instead a SERVFAIL should come back.

Note: we should also validate the date... but we should correct the server's handling of error cases before we correct the case that causes an error.