Stream to log

@vezzi I think this will log all the Piper output via the standard minimal_logger we use for everything else. I couldn't test it because nestor is being funky and I think there's some permissions issue. Maybe you can try it out or I'll give it another shot on Monday.
I did not check that! Looks cool especially in combination with the TimedRotatingFileHandler as shown here: https://gist.github.com/matagus/652785