Use svg for build status directly from travis-ci

Since there is no reason to use shields for the build status badge we can use it directly from travis-ci

README.md

@@ -1,4 +1,4 @@
-# Monolog - Logging for PHP [![Build Status](https://img.shields.io/travis/Seldaek/monolog.svg)](https://travis-ci.org/Seldaek/monolog)
+# Monolog - Logging for PHP [![Build Status](https://travis-ci.org/Seldaek/monolog.svg?branch=master)](https://travis-ci.org/Seldaek/monolog)
 
 [![Total Downloads](https://img.shields.io/packagist/dt/monolog/monolog.svg)](https://packagist.org/packages/monolog/monolog)
 [![Latest Stable Version](https://img.shields.io/packagist/v/monolog/monolog.svg)](https://packagist.org/packages/monolog/monolog)