Add NATS output plugin.

Added NATS server container needed for tests.

Added NATS output plug-in. Fixes #1487

NATS output plug-in use internal.GetTLSConfig to instrument TLS configuration.

Added NATS output plug-in to changelog.

closes #1487
closes #1697

plugins/outputs/nats/nats_test.go

@@ -0,0 +1,31 @@
+package nats
+
+import (
+	"testing"
+
+	"github.com/influxdata/telegraf/plugins/serializers"
+	"github.com/influxdata/telegraf/testutil"
+	"github.com/stretchr/testify/require"
+)
+
+func TestConnectAndWrite(t *testing.T) {
+	if testing.Short() {
+		t.Skip("Skipping integration test in short mode")
+	}
+
+	server := []string{"nats://" + testutil.GetLocalHost() + ":4222"}
+	s, _ := serializers.NewInfluxSerializer()
+	n := &NATS{
+		Servers:    server,
+		Subject:    "telegraf",
+		serializer: s,
+	}
+
+	// Verify that we can connect to the NATS daemon
+	err := n.Connect()
+	require.NoError(t, err)
+
+	// Verify that we can successfully write data to the NATS daemon
+	err = n.Write(testutil.MockMetrics())
+	require.NoError(t, err)
+}