Add wlan station and interface metrics collection. (#14)

* Fix newlines.
* Added wlan metrics.
* Fix WlanSTA collector - return on errors.

collector/helper.go

@@ -1,6 +1,8 @@
 package collector
 
 import (
+	"math"
+	"strconv"
 	"strings"
 
 	"github.com/prometheus/client_golang/prometheus"
@@ -27,3 +29,17 @@ func description(prefix, name, helpText string, labelNames []string) *prometheus
 		nil,
 	)
 }
+
+func splitStringToFloats(metric string) (float64, float64, error) {
+	strings := strings.Split(metric, ",")
+
+	m1, err := strconv.ParseFloat(strings[0], 64)
+	if err != nil {
+		return math.NaN(), math.NaN(), err
+	}
+	m2, err := strconv.ParseFloat(strings[1], 64)
+	if err != nil {
+		return math.NaN(), math.NaN(), err
+	}
+	return m1, m2, nil
+}