Rewriting Riemann output plugin (#1900)

* rename to riemann_legacy

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* initial draft for Riemann output plugin rewrite

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* add unit tests

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* add option to send string metrics as states

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* add integration tests

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* add plugin README.md

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* bump riemann library

* clarify settings description

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* update Readme.md with updated description

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* add Riemann event examples

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

* use full URL for Riemann server address

Signed-off-by: Fabio Berchtold <fabio.berchtold@swisscom.com>

closes #1878

plugins/outputs/riemann_legacy/riemann_test.go

@@ -0,0 +1,27 @@
+package riemann_legacy
+
+import (
+	"testing"
+
+	"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")
+	}
+
+	url := testutil.GetLocalHost() + ":5555"
+
+	r := &Riemann{
+		URL:       url,
+		Transport: "tcp",
+	}
+
+	err := r.Connect()
+	require.NoError(t, err)
+
+	err = r.Write(testutil.MockMetrics())
+	require.NoError(t, err)
+}