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/sha3/xor.go

@@ -1,16 +0,0 @@
-// Copyright 2015 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,!ppc64le appengine
-
-package sha3
-
-var (
-	xorIn            = xorInGeneric
-	copyOut          = copyOutGeneric
-	xorInUnaligned   = xorInGeneric
-	copyOutUnaligned = copyOutGeneric
-)
-
-const xorImplementationUnaligned = "generic"