src/ScraperPromise.js
function(callback) {
		this.promises.push(function async(done, utils) {
			callback(utils.lastReturn, done, utils);
		});
		return this;
	}
function(callback) {
		this.promises.push(function async(done, utils) {
			callback(utils.lastReturn, done, utils);
		});
		return this;
	}
function ( callback ) { this . promises . push ( function async ( done , utils ) { callback ( utils . lastReturn , done , utils ) ; } ) ; return this ; }
Stops the promise chain and resumes it after a callback
function.

@param  {!function(!function, !Object)} callback Callback.
@return {!ScraperPromise} This object, so that new promises can
be made.
@public
Stops the promise chain and resumes it after a callback function .