network_utils.stun_servers_status_report(server_list)

Given a list of stun servers, probes them and prints out
a report. Useful whenever we want to update the list of
STUN servers to use.
updated STUN server list.
Merge pull request #2 from gubatron/fix_STUN_check

network_utils.stun_servers_status_report(server_list)