message: dont limit output value to minValue. throw error when timeConstant <= 0
diff: @@ -289,10 +289,9 @@ define(["Tone/core/Tone", "Tone/type/Type"], function(Tone){
  Tone.Param.prototype.setTargetAtTime = function(value, startTime, timeConstant){
  value = this._fromUnits(value);
  // The value will never be able to approach without timeConstant > 0.
  - // http://www.w3.org/TR/webaudio/#dfn-setTargetAtTime, where the equation
  - // is described. 0 results in a division by 0.
  - value = Math.max(this._minOutput, value);
  - timeConstant = Math.max(this._minOutput, timeConstant);
  + if (timeConstant <= 0){
  + throw new Error("timeConstant must be greater than 0");
  + }
  this._param.setTargetAtTime(value, this.toSeconds(startTime), timeConstant);
  return this;
  };
  