Remove travis (#509)

.travis.yml

@@ -1,5 +0,0 @@
-language: java
-jdk:
-    - openjdk11
-after_success:
-  - mvn clean cobertura:cobertura coveralls:report

README.md

@@ -3,7 +3,7 @@
 Plugin Framework for Java (PF4J)
 =====================
 [![Join the chat at https://gitter.im/decebals/pf4j](https://badges.gitter.im/decebals/pf4j.svg)](https://gitter.im/decebals/pf4j?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
-[![Travis CI Build Status](https://travis-ci.org/pf4j/pf4j.png)](https://travis-ci.org/pf4j/pf4j)
+[![GitHub Actions Status](https://github.com/pf4j/pf4j/actions/workflows/build.yml/badge.svg)](https://github.com/pf4j/pf4j/actions/workflows/build.yml)
 [![Coverage Status](https://coveralls.io/repos/pf4j/pf4j/badge.svg?branch=master&service=github)](https://coveralls.io/github/pf4j/pf4j?branch=master)
 [![Maven Central](http://img.shields.io/maven-central/v/org.pf4j/pf4j.svg)](http://search.maven.org/#search|ga|1|pf4j)