Draw the Button into its canvas context using the current .__value property and button style.
@memberof Button
@instance
function draw() {
    this.ctx.fillStyle = this.__value === 1 ? this.fill : this.background;
    this.ctx.strokeStyle = this.stroke;
    this.ctx.lineWidth = this.lineWidth;
    this.ctx.fillRect(0, 0, this.rect.width, this.rect.height);

    this.ctx.strokeRect(0, 0, this.rect.width, this.rect.height);
  }