Add download count badge

Author: colinodell

README.md

@@ -1,6 +1,7 @@
 # Unleashed Technologies PHP_CodeSniffer Coding Standard
 
 [![Latest Version](https://img.shields.io/packagist/v/unleashedtech/php-coding-standard.svg?style=flat-square)](https://packagist.org/packages/unleashedtech/php-coding-standard)
+[![Total Downloads](https://img.shields.io/packagist/dt/unleashedtech/php-coding-standard.svg?style=flat-square)](https://packagist.org/packages/unleashedtech/php-coding-standard)
 [![Build Status](https://img.shields.io/travis/unleashedtech/php-coding-standard/master.svg?style=flat-square)](https://travis-ci.org/unleashedtech/php-coding-standard)
 [![Software License](https://img.shields.io/badge/License-MIT-brightgreen.svg?style=flat-square)](LICENSE)