Tail remote logs live

Make 'lymph tail' able to connect and disconnect from service and they
come and go, and that by making lymph.core.services.Service class
implement an Observable interface, that the newly introduced class
RemoteTail will use to observe when services get added or removed,
and react by connecting and disconnecting from this later respectively.
For me it big red point when super is called with a different signature that the method calling it, because this break multiple inheritance big time ! more info in the famous blog entry from Raymond Hettinger http://rhettinger.wordpress.com/2011/05/26/super-considered-super/.