move plugin interfaces into separate package

plugins/serializers/graphite/graphite.go

@@ -5,7 +5,7 @@ import (
 	"sort"
 	"strings"
 
-	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins"
 )
 
 const DEFAULT_TEMPLATE = "host.tags.measurement.field"
@@ -20,7 +20,7 @@ type GraphiteSerializer struct {
 	Template string
 }
 
-func (s *GraphiteSerializer) Serialize(metric telegraf.Metric) ([]byte, error) {
+func (s *GraphiteSerializer) Serialize(metric plugins.Metric) ([]byte, error) {
 	out := []byte{}
 
 	// Convert UnixNano to Unix timestamps

plugins/serializers/influx/influx.go

@@ -1,12 +1,12 @@
 package influx
 
 import (
-	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins"
 )
 
 type InfluxSerializer struct {
 }
 
-func (s *InfluxSerializer) Serialize(m telegraf.Metric) ([]byte, error) {
+func (s *InfluxSerializer) Serialize(m plugins.Metric) ([]byte, error) {
 	return m.Serialize(), nil
 }

plugins/serializers/json/json.go

@@ -3,13 +3,13 @@ package json
 import (
 	ejson "encoding/json"
 
-	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins"
 )
 
 type JsonSerializer struct {
 }
 
-func (s *JsonSerializer) Serialize(metric telegraf.Metric) ([]byte, error) {
+func (s *JsonSerializer) Serialize(metric plugins.Metric) ([]byte, error) {
 	m := make(map[string]interface{})
 	m["tags"] = metric.Tags()
 	m["fields"] = metric.Fields()

plugins/serializers/registry.go

@@ -1,7 +1,7 @@
 package serializers
 
 import (
-	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins"
 
 	"github.com/influxdata/telegraf/plugins/serializers/graphite"
 	"github.com/influxdata/telegraf/plugins/serializers/influx"
@@ -21,7 +21,7 @@ type Serializer interface {
 	// Serialize takes a single telegraf metric and turns it into a byte buffer.
 	// separate metrics should be separated by a newline, and there should be
 	// a newline at the end of the buffer.
-	Serialize(metric telegraf.Metric) ([]byte, error)
+	Serialize(metric plugins.Metric) ([]byte, error)
 }
 
 // Config is a struct that covers the data types needed for all serializer types,