add rubocop binstub [ci skip]

#!/usr/bin/env ruby

#

# This file was generated by Bundler.

#

# The application 'rubocop' is installed as part of a gem, and

# this file is here to facilitate running it.

#

require 'pathname'

ENV['BUNDLE_GEMFILE'] ||= File.expand_path("../../Gemfile",

  Pathname.new(__FILE__).realpath)

require 'rubygems'

require 'bundler/setup'

load Gem.bin_path('rubocop', 'rubocop')