ClientStub and improved rspec helpers

lib/telegram/bot.rb

@@ -8,6 +8,7 @@ module Telegram
     class NotFound < Error; end
 
     autoload :Client,             'telegram/bot/client'
+    autoload :ClientStub,         'telegram/bot/client_stub'
     autoload :Middleware,         'telegram/bot/middleware'
     autoload :UpdatesController,  'telegram/bot/updates_controller'
     autoload :UpdatesPoller,      'telegram/bot/updates_poller'