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/topk/topk_test.go

@@ -0,0 +1,57 @@
+package topk
+
+import (
+	"fmt"
+	"math/rand"
+	"sort"
+	"testing"
+)
+
+func TestTopK(t *testing.T) {
+	stream := New(10)
+	ss := []*Stream{New(10), New(10), New(10)}
+	m := make(map[string]int)
+	for _, s := range ss {
+		for i := 0; i < 1e6; i++ {
+			v := fmt.Sprintf("%x", int8(rand.ExpFloat64()))
+			s.Insert(v)
+			m[v]++
+		}
+		stream.Merge(s.Query())
+	}
+
+	var sm Samples
+	for x, s := range m {
+		sm = append(sm, &Element{x, s})
+	}
+	sort.Sort(sort.Reverse(sm))
+
+	g := stream.Query()
+	if len(g) != 10 {
+		t.Fatalf("got %d, want 10", len(g))
+	}
+	for i, e := range g {
+		if sm[i].Value != e.Value {
+			t.Errorf("at %d: want %q, got %q", i, sm[i].Value, e.Value)
+		}
+	}
+}
+
+func TestQuery(t *testing.T) {
+	queryTests := []struct {
+		value string
+		expected int
+	}{
+		{"a", 1},
+		{"b", 2},
+		{"c", 2},
+	}
+
+	stream := New(2)
+	for _, tt := range queryTests {
+		stream.Insert(tt.value)
+		if n := len(stream.Query()); n != tt.expected {
+			t.Errorf("want %d, got %d", tt.expected, n)
+		}
+	}
+}