Read and write packets with multiple questions for mDNS

[kmpm]

Full roundtrip does not work because of lacking utf-8 support.

[kmpm]

This will close #14.
The fixture files added are examples from 2 chromecast devices and 1 netgear readynas.
So packets without question and multiple questions are definitely out in the wild.
But it's only for mDNS/zeroconf applications.

[taoeffect]

Interesting, thank you, will need to find time for review. @tjfontaine @silverwind or anyone else feel free to check this out if you have the time. Looks very useful! 👍

[silverwind]

Not familar with mDNS yet, but it's interesting.

[kmpm]

I would like to have this included but I don't know what to do to help out.
What this does is to support what is described in http://tools.ietf.org/html/rfc1035
Look at section 4.1.1. Header section format and 4.1.2. Question section format.

QDCOUNT         an unsigned 16 bit integer specifying the number of
                entries in the question section.

The section contains QDCOUNT (usually 1) entries

This is necessary for being able to use this module for RFC 6734 "DNS-Based Service Descovery" and RFC 6762 "Multicast DNS". This doesn't require anything strange in the message format. It's using the existing DNS message structure, name syntax, and resource record types as RFC 1035.

If there are any code style issues, bad practice or anything else with the code I'll gladly fix it but I would like some feedback