Use svg travis build badge

Author: britter

README.md

@@ -1,6 +1,6 @@
 spring-boot-admin
 =================
-[![Build Status](https://travis-ci.org/codecentric/spring-boot-admin.png?branch=master)](https://travis-ci.org/codecentric/spring-boot-admin)
+[![Build Status](https://travis-ci.org/codecentric/spring-boot-admin.svg)](https://travis-ci.org/codecentric/spring-boot-admin)
 [![Coverage Status](https://coveralls.io/repos/codecentric/spring-boot-admin/badge.svg)](https://coveralls.io/r/codecentric/spring-boot-admin)
 [![Maven Central](https://maven-badges.herokuapp.com/maven-central/de.codecentric/spring-boot-admin/badge.svg)](https://maven-badges.herokuapp.com/maven-central/de.codecentric/spring-boot-admin/)
 [![Gitter](https://badges.gitter.im/Join Chat.svg)](https://gitter.im/codecentric/spring-boot-admin?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)