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/poly1305/sum_amd64.go

@@ -1,22 +0,0 @@
-// Copyright 2012 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,!gccgo,!appengine
-
-package poly1305
-
-// This function is implemented in sum_amd64.s
-//go:noescape
-func poly1305(out *[16]byte, m *byte, mlen uint64, key *[32]byte)
-
-// Sum generates an authenticator for m using a one-time key and puts the
-// 16-byte result into out. Authenticating two different messages with the same
-// key allows an attacker to forge messages at will.
-func Sum(out *[16]byte, m []byte, key *[32]byte) {
-	var mPtr *byte
-	if len(m) > 0 {
-		mPtr = &m[0]
-	}
-	poly1305(out, mPtr, uint64(len(m)), key)
-}