added json serializer

closes #878

plugins/serializers/json/json.go

@@ -0,0 +1,27 @@
+package json
+
+import (
+	ejson "encoding/json"
+
+	"github.com/influxdata/telegraf"
+)
+
+type JsonSerializer struct {
+}
+
+func (s *JsonSerializer) Serialize(metric telegraf.Metric) ([]string, error) {
+	out := []string{}
+
+	m := make(map[string]interface{})
+	m["tags"] = metric.Tags()
+	m["fields"] = metric.Fields()
+	m["name"] = metric.Name()
+	m["timestamp"] = metric.UnixNano() / 1000000000
+	serialized, err := ejson.Marshal(m)
+	if err != nil {
+		return []string{}, err
+	}
+	out = append(out, string(serialized))
+
+	return out, nil
+}