chg: 把optScanHandlers改到options.scanners, 便于扩展.
chg: 把扫描器命名空间加到全局命名空间, 便于扩展.
Merge branch 'chg-scanner' 把options.scanners改到exports.scanners

Conflicts:
	src/handlers.js
	src/scan.js
chg: 把事件绑定属性加到参数options上, 便于配置.