function PosePredictor(predictionTimeS) {
  this.predictionTimeS = predictionTimeS;

  // The quaternion corresponding to the previous state.
  this.previousQ = new MathUtil.Quaternion();
  // Previous time a prediction occurred.
  this.previousTimestampS = null;

  // The delta quaternion that adjusts the current pose.
  this.deltaQ = new MathUtil.Quaternion();
  // The output quaternion.
  this.outQ = new MathUtil.Quaternion();
}
Given an orientation and the gyroscope data, predicts the future orientation
of the head. This makes rendering appear faster.

Also see: http://msl.cs.uiuc.edu/~lavalle/papers/LavYerKatAnt14.pdf

@param {Number} predictionTimeS time from head movement to the appearance of
the corresponding image.