扫描特定的信标

 beacon = CLBeaconRegion(proximityUUID: <#NSUUID#>, major: <#CLBeaconMajorValue#>, identifier: <#String#>) // listening to all beacons with given UUID and major value
 beacon =    CLBeaconRegion(proximityUUID: <##NSUUID#>, major: <##CLBeaconMajorValue#>, minor: <##CLBeaconMinorValue#>, identifier: <##String#>) // listening to all beacons with given UUID and major and minor value