deploytool: Add README.md, migrate docs to it.

deploytool/cmd/luci_deploy/version.go

 // Copyright 2016 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package main
 
 import (
         "os/user"
         "strings"
 
@@ skipping 107 matching lines @@
 func cloudVersionStringNormalize(v string) string {
         return strings.Map(func(r rune) rune {
                 if (r >= 'a' && r <= 'z') ||
                         (r >= 'A' && r <= 'Z') ||
                         (r >= '0' && r <= '9') {
                         return r
                 }
                 return '_'
         }, v)
 }