Initial delivery of metrics code (#81)

* Initial delivery of metrics code

* Fix build issues

* Fix build issue with go vet

vendor/golang.org/x/crypto/blake2s/blake2s_ref.go

@@ -1,17 +0,0 @@
-// Copyright 2016 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build !amd64,!386 gccgo appengine
-
-package blake2s
-
-var (
-	useSSE4  = false
-	useSSSE3 = false
-	useSSE2  = false
-)
-
-func hashBlocks(h *[8]uint32, c *[2]uint32, flag uint32, blocks []byte) {
-	hashBlocksGeneric(h, c, flag, blocks)
-}