Initial delivery of metrics code (#81)

* Initial delivery of metrics code

* Fix build issues

* Fix build issue with go vet

vendor/github.com/beorn7/perks/histogram/histogram_test.go

@@ -0,0 +1,38 @@
+package histogram
+
+import (
+	"math/rand"
+	"testing"
+)
+
+func TestHistogram(t *testing.T) {
+	const numPoints = 1e6
+	const maxBins = 3
+
+	h := New(maxBins)
+	for i := 0; i < numPoints; i++ {
+		f := rand.ExpFloat64()
+		h.Insert(f)
+	}
+
+	bins := h.Bins()
+	if g := len(bins); g > maxBins {
+		t.Fatalf("got %d bins, wanted <= %d", g, maxBins)
+	}
+
+	for _, b := range bins {
+		t.Logf("%+v", b)
+	}
+
+	if g := count(h.Bins()); g != numPoints {
+		t.Fatalf("binned %d points, wanted %d", g, numPoints)
+	}
+}
+
+func count(bins Bins) int {
+	binCounts := 0
+	for _, b := range bins {
+		binCounts += b.Count
+	}
+	return binCounts
+}