disable dnsmasq and use --dns

[benbro]

In ubuntu 14.04 desktop I need to disable dnsmasq by commenting "dns=dnsmasq" in /etc/NetworkManager/NetworkManager.conf

I think that the readme should explain that other containers that want to access the rawdns service need to pass the docker0 host ip
--dns

[tianon]

Yeah, documenting whole-machine DNS takeover better is something I'm definitely keen to see here (especially telling NetworkManager to not overwrite "resolv.conf" -- I have to look that up myself every time I set up a new machine).