Add badges

Author: baymac

README.md

@@ -1,3 +1,8 @@
+[![Build Status](https://ci.jenkins.io/job/Plugins/job/gitlab-api-plugin/job/master/badge/icon)](https://ci.jenkins.io/job/Plugins/job/gitlab-api-plugin/job/master/)
+[![GitHub release](https://img.shields.io/github/release/jenkinsci/gitlab-api-plugin.svg?label=release)](https://github.com/jenkinsci/gitlab-api-plugin/releases/latest)
+[![Gitter](https://badges.gitter.im/jenkinsci/gitlab-branch-source-plugin.svg)](https://gitter.im/jenkinsci/gitlab-branch-source-plugin)
+[![Jenkins Plugin Installs](https://img.shields.io/jenkins/plugin/i/gitlab-api.svg?color=blue)](https://plugins.jenkins.io/gitlab-api)
+
 # gitlab-api-plugin
 Wraps [Gitlab Java API](https://github.com/gmessner/gitlab4j-api/) by [gmessner](https://github.com/gmessner) into a plugin