Fix some formatting issues

Author: MrLotU

Sources/Prometheus/MetricTypes/Counter.swift

@@ -25,7 +25,9 @@ public class Counter<NumType: Numeric, Labels: MetricLabels>: Metric, Prometheus
 
         output.append(headers)
 
-        output.append("\(name) \(value)")
+        if value != initialValue && initialValue == 0 {
+            output.append("\(name) \(value)")
+        }
 
         metrics.forEach { (labels, value) in
             let labelsString = encodeLabels(labels)

Sources/Prometheus/MetricTypes/Gauge.swift

@@ -25,7 +25,9 @@ public class Gauge<NumType: Numeric, Labels: MetricLabels>: Metric, PrometheusHa
 
         output.append(headers)
 
-        output.append("\(name) \(value)")
+        if value != initialValue && initialValue == 0 {
+            output.append("\(name) \(value)")
+        }
 
         metrics.forEach { (labels, value) in
             let labelsString = encodeLabels(labels)