AbstractScraper = function() {
	/**
	 * Status code of the last requested page.
	 *
	 * @type {!number}
	 * @protected
	 */
	this.statusCode = null;
	/**
	 * Response of the last requested page.
	 *
	 * @type {!Object}
	 * @protected
	 */
	this.response = null;
	/**
	 * Body of the last webpage, as a string.
	 *
	 * @type {!string}
	 * @protected
	 */
	this.body = null;
	/**
	 * URL.
	 *
	 * @type {!string}
	 * @protected
	 */
	this.url = '';
}
An abstract scraper, this class should not be used directly as a
  scraper, instead a concrete scraper should inherit or use this
  class as a composite this class.

@constructor