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

deploytool/cmd/luci_deploy/kubernetes.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 (
         "fmt"
         "sort"
 
@@ skipping 420 matching lines @@
         case rv != 0:
                 return errKubeResourceNotFound
 
         default:
                 if err := yaml.Unmarshal(x.stdout.Bytes(), obj); err != nil {
                         return errors.Annotate(err).Reason("failed to unmarshal YAML %(type)T").D("type", obj).Err()
                 }
                 return nil
         }
 }