Add support for Datadog distribution type

This adds the ability to accept Datadog's distribution type and treat it
like a histogram/summary.

Signed-off-by: Clayton O'Neill <claytono@github.com>

README.md

@@ -224,6 +224,8 @@ mappings:
     job: "${1}_server"
 ```
 
+Note that timers will be accepted with the `ms`, `h`, and `d` statsd types.  The first two are timers and histograms and the `d` type is for DataDog's "distribution" type.  The distribution type is treated identically to timers and histograms.
+
 ### Regular expression matching
 
 Another capability when using YAML configuration is the ability to define matches

bridge_test.go

@@ -67,6 +67,26 @@ func TestHandlePacket(t *testing.T) {
 					labels:     map[string]string{},
 				},
 			},
+		}, {
+			name: "simple histogram",
+			in:   "foo:200|h",
+			out: Events{
+				&TimerEvent{
+					metricName: "foo",
+					value:      200,
+					labels:     map[string]string{},
+				},
+			},
+		}, {
+			name: "simple distribution",
+			in:   "foo:200|d",
+			out: Events{
+				&TimerEvent{
+					metricName: "foo",
+					value:      200,
+					labels:     map[string]string{},
+				},
+			},
 		}, {
 			name: "datadog tag extension",
 			in:   "foo:100|c|#tag1:bar,tag2:baz",

exporter.go

@@ -571,7 +571,7 @@ func buildEvent(statType, metric string, value float64, relative bool, labels ma
 			relative:   relative,
 			labels:     labels,
 		}, nil
-	case "ms", "h":
+	case "ms", "h", "d":
 		return &TimerEvent{
 			metricName: metric,
 			value:      float64(value),