Destroy the cropper and remove the instance from the image
@returns {Cropper} this
function destroy() {
    var element = this.element;

    if (!element[NAMESPACE]) {
      return this;
    }

    element[NAMESPACE] = undefined;

    if (this.isImg && this.replaced) {
      element.src = this.originalUrl;
    }

    this.uncreate();
    return this;
  }