Add version to the readme (telegramdesktop#2635)

Its updated by adding tags

README.md

@@ -2,6 +2,7 @@
 
 This is the complete source code and the build instructions for the alpha version of the official desktop client for the [Telegram][telegram] messenger, based on the [Telegram API][telegram_api] and the [MTProto][telegram_proto] secure protocol.
 
+[![GitHub version](https://badge.fury.io/gh/telegramdesktop%2Ftdesktop.svg)](https://badge.fury.io/gh/telegramdesktop%2Ftdesktop)
 [![Build Status](https://travis-ci.org/telegramdesktop/tdesktop.svg?branch=master)](https://travis-ci.org/telegramdesktop/tdesktop)
 
 The source code is published under GPLv3 with OpenSSL exception, the license is available [here][license].