Fix Prometheus collector

Now that we fetch the forecast too we need to ensure we only process
today's value. Tomorrow at the same time might have the same price which
will lead to errors.

Author: daenney

prometheus.go

@@ -39,6 +39,9 @@ func (v *vattenfallCollector) Collect(ch chan<- prometheus.Metric) {
 			log.Println(err)
 		}
 		for _, entry := range data {
+			if entry.Timestamp.Day() != now.Day() {
+				continue
+			}
 			if entry.Timestamp.Hour() == now.Hour() {
 				ch <- prometheus.MustNewConstMetric(v.prices,
 					prometheus.GaugeValue, entry.Value, entry.Region)