[skip ci] update travis ci badge from .org to .com

Author: jsvd

README.md

@@ -1,6 +1,6 @@
 # Logstash Plugin
 
-[![Travis Build Status](https://travis-ci.org/logstash-plugins/logstash-input-kafka.svg)](https://travis-ci.org/logstash-plugins/logstash-input-kafka)
+[![Travis Build Status](https://travis-ci.com/logstash-plugins/logstash-input-kafka.svg)](https://travis-ci.com/logstash-plugins/logstash-input-kafka)
 
 This is a plugin for [Logstash](https://github.com/elastic/logstash).