Add notifications by webhook.

Add a new config entry moving to version 13.
```
		"webhook": {
			"1": {
				"enable": true,
				"address": "http://requestb.in/1i9al7m1"
			}
		}
```

cmd/notify-amqp.go

@@ -82,7 +82,7 @@ func newAMQPNotify(accountID string) (*logrus.Logger, error) {
 	return amqpLog, nil
 }
 
-// Fire is called when an event should be sent to the message broker.k
+// Fire is called when an event should be sent to the message broker.
 func (q amqpConn) Fire(entry *logrus.Entry) error {
 	ch, err := q.Connection.Channel()
 	if err != nil {