message: compute time string values for envelope attack/release
  fixes
diff: @@ -85,7 +85,7 @@ Tone.Synth.prototype._triggerEnvelopeAttack = function(time, velocity){
  this.oscillator.start(time);
  //if there is no release portion, stop the oscillator
  if (this.envelope.sustain === 0){
  - this.oscillator.stop(time + this.envelope.attack + this.envelope.decay);
  + this.oscillator.stop(time + this.toSeconds(this.envelope.attack) + this.toSeconds(this.envelope.decay));
  }
  return this;
  };
  @@ -99,7 +99,7 @@ Tone.Synth.prototype._triggerEnvelopeAttack = function(time, velocity){
  Tone.Synth.prototype._triggerEnvelopeRelease = function(time){
  time = this.toSeconds(time);
  this.envelope.triggerRelease(time);
  - this.oscillator.stop(time + this.envelope.release);
  + this.oscillator.stop(time + this.toSeconds(this.envelope.release));
  return this;
  };
  