Update NetworkInfo to work with Thunderbolt Ethernet (Macbook Air and Retinas)

On retina MBPs, the ethernet is slightly different.  Here's the network services on my rMBP:

> networksetup -listallnetworkservices
An asterisk (*) denotes that a network service is disabled.
Thunderbolt Ethernet
Wi-Fi
Thunderbolt Bridge
VPN (PPTP)
Witopia KC IPsec
Bluetooth DUN
Bluetooth PAN