startTimer() {
    return new Profiler(this);
  }
Returns an object corresponding to a specific timing. When done is called
the timer will finish and log the duration. e.g.:
@returns {Profile} - TODO: add return description.
@example
   const timer = winston.startTimer()
   setTimeout(() => {
     timer.done({
       message: 'Logging message'
     });
   }, 1000);