Update readme

README.md

@@ -1,6 +1,8 @@
-# TOTP [![Build Status][travis-image]][travis-url] [![Coverage Status][coveralls-image]][coveralls-url]
+# TOTP ![PHP 5.6+][php-image] [![Build Status][travis-image]][travis-url] [![Coverage Status][coveralls-image]][coveralls-url] [![Packagist][packagist-image]][packagist-url]
 
-A PHP library for TOTP support in PHP 5.6+.
+A PHP library for generating one-time passwords according to [RFC-6238](http://tools.ietf.org/html/rfc6238) for time-based OTP generation.
+
+This library is compatible with Google Authenticator apps available for Android and iPhone.
 
 ## Quick Start
 
@@ -23,6 +25,9 @@ if (EAMann\TOTP\is_valid_auth_code($token, $otp)) {
 ```
 
 
+[php-image]: https://img.shields.io/badge/php-5.6%2B-green.svg
+[packagist-image]: https://img.shields.io/packagist/dt/ericmann/totp.svg
+[packagist-url]: https://packagist.org/packages/ericmann/totp
 [travis-image]: https://travis-ci.org/ericmann/totp.svg?branch=master
 [travis-url]: https://travis-ci.org/ericmann/totp
 [coveralls-image]: https://coveralls.io/repos/github/ericmann/totp/badge.svg?branch=master