Fixed spelling error in call to Log.warn (fixes crash on OSX).  Added
--udp-port option to set port for shared STUN/uTP UDP socket.
Fixed --udp-port help text.  Added Connection.authenticated?, used by
ConnectionManager in have_connection? instead of non-existent active?.
inotify not available on OSX, use fsevent instead.
Merge pull request #18 from chipselecta/master

file monitoring on OSX + minor changes