Update README.md

Update 6.1 Rails.

Author: florentferry

README.md

@@ -596,11 +596,7 @@ A Rails controller that allows a user to authorize their GitHub account and then
 ```ruby
 class GithubController < ApplicationController
 
-  attr_accessor :github
-  private :github
-
   def authorize
-    github  = Github.new client_id: '...', client_secret: '...'
     address = github.authorize_url redirect_uri: 'http://...', scope: 'repo'
     redirect_to address
   end
@@ -610,6 +606,12 @@ class GithubController < ApplicationController
     access_token = github.get_token authorization_code
     access_token.token   # => returns token value
   end
+  
+  private
+  
+   def github
+    @github ||= Github.new client_id: '...', client_secret: '...'
+   end
 end
 ```