Support http service graceful restart (#416)

* support http service graceful restart

* fix dependencies

vendor/github.com/facebookgo/stats/stopper.go

@@ -0,0 +1,17 @@
+package stats
+
+import "time"
+
+// Stopper calls Client.BumpSum and Client.BumpHistogram when End'ed
+type Stopper struct {
+	Key    string
+	Start  time.Time
+	Client Client
+}
+
+// End the Stopper
+func (s *Stopper) End() {
+	since := time.Since(s.Start).Seconds() * 1000.0
+	s.Client.BumpSum(s.Key+".total", since)
+	s.Client.BumpHistogram(s.Key, since)
+}