#216 add AtBot event !219
Created by: lijiarui
I added an event called 'message-at', once the event is emitted, it will return:
who in where @bot said what
the following code works well.
.on('message-at', function(contact, room, content) {
console.log('message-at event works!')
console.log(contact)
console.log(room)
console.log(content)
})