Update README with new badge and remove outdated info

Author: wxmerkt

README.md

@@ -1,10 +1,6 @@
-octomap_mapping [![Build Status](https://travis-ci.org/OctoMap/octomap_mapping.svg?branch=kinetic-devel)](https://travis-ci.org/OctoMap/octomap_mapping)
+octomap_mapping ![CI](https://github.com/OctoMap/octomap_mapping/workflows/CI/badge.svg)
 ===============
 
 ROS stack for mapping with OctoMap, contains the `octomap_server` package.
 
-The main branch for Kinetic, Melodic, and Noetic is `kinetic-devel`.
-
-Indigo: [![Build Status](https://travis-ci.org/OctoMap/octomap_mapping.svg?branch=indigo-devel)](https://travis-ci.org/OctoMap/octomap_mapping)
-
-Imported from SVN, see https://code.google.com/p/alufr-ros-pkg/ for the previous versions.
+The main branch for ROS Kinetic and newer is `kinetic-devel`.