Remove HHVM build status

Image was broken and we don’t support modern HHVM anyway…

Author: sabberworm

README.md

@@ -1,7 +1,7 @@
 PHP CSS Parser
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-[![build status](https://api.travis-ci.org/sabberworm/PHP-CSS-Parser.svg)](https://travis-ci.org/sabberworm/PHP-CSS-Parser) [![HHVM Status](http://hhvm.h4cc.de/badge/sabberworm/php-css-parser.svg)](http://hhvm.h4cc.de/package/sabberworm/php-css-parser)
+[![build status](https://api.travis-ci.org/sabberworm/PHP-CSS-Parser.svg)](https://travis-ci.org/sabberworm/PHP-CSS-Parser)
 
 A Parser for CSS Files written in PHP. Allows extraction of CSS files into a data structure, manipulation of said structure and output as (optimized) CSS.