New methods from bot api v3.5

Collect all api helper-methods in Client::ApiHelper module.
Add bin/fetch-telegram-methods to update methods list from website.

lib/telegram/bot/version.rb

@@ -1,6 +1,6 @@
 module Telegram
   module Bot
-    VERSION = '0.12.1'.freeze
+    VERSION = '0.12.3'.freeze
 
     def self.gem_version
       Gem::Version.new VERSION