completed CiscoNexus.parse_cdp function. will check to see if it can parse cisco
ios and iox and ucs cdp info.
add a new inheritance.. ciscoios, cisco_iox, cisco_nexus all inherit from
cisco_network_device, which inherits network_device

plan on moving parse_cdp to cisco_network_device since it "should" work on all
cisco network devices..(not thinking of firewalls right now)