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

deploytool/cmd/luci_deploy/title.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 (
         "path/filepath"
         "unicode"
 
@@ skipping 27 matching lines @@
         path = filepath.Base(path)
         if filepath.Ext(path) == configExt {
                 t := title(path[:len(path)-len(configExt)])
                 if err := t.validate(); err != nil {
                         return "", err
                 }
                 return t, nil
         }
         return "", errors.Reason("missing config extension [" + configExt + "]").Err()
 }