Doesn't resolve SRV records

[geraintwhite]

This module does not resolve SRV records like the node.js dns module does.

> dns.resolve('_sip._udp.ipcomms-btwmetrocore-moda.bt.com', 'SRV', console.log)
> null [ { name: 'ipcomms-btwmetro201-moda.bt.com',
    port: 5060,
    priority: 10,
    weight: 20 },
  { name: 'ipcomms-btwcore203-moda.bt.com',
    port: 5060,
    priority: 20,
    weight: 20 } ]

> dnsjs = require('dns.js')
> dnsjs.resolve('_sip._udp.ipcomms-btwmetrocore-moda.bt.com', 'SRV', console.log)
> null []