Fix URL to download counter in README

Author: mikehaertl

README.md

@@ -3,7 +3,7 @@ php-shellcommand
 
 [![Build Status](https://secure.travis-ci.org/mikehaertl/php-shellcommand.png)](http://travis-ci.org/mikehaertl/php-shellcommand)
 [![Latest Stable Version](https://poser.pugx.org/mikehaertl/php-shellcommand/v/stable.svg)](https://packagist.org/packages/mikehaertl/php-shellcommand)
-[![Total Downloads](https://poser.pugx.org/mikehaertl/php-shellcommand/downloads.svg)](https://packagist.org/packages/mikehaertl/php-shellcommand)
+[![Total Downloads](https://poser.pugx.org/mikehaertl/php-shellcommand/downloads)](https://packagist.org/packages/mikehaertl/php-shellcommand)
 [![Latest Unstable Version](https://poser.pugx.org/mikehaertl/php-shellcommand/v/unstable.svg)](https://packagist.org/packages/mikehaertl/php-shellcommand)
 [![HHVM Status](http://hhvm.h4cc.de/badge/mikehaertl/php-shellcommand.png)](http://hhvm.h4cc.de/package/mikehaertl/php-shellcommand)
 [![License](https://poser.pugx.org/mikehaertl/php-shellcommand/license.svg)](https://packagist.org/packages/mikehaertl/php-shellcommand)