Update to CP 5.5 for newer confluent-librdkafka-plugins

Author: edenhill

.travis.yml

@@ -16,7 +16,7 @@ env:
     - LIBRDKAFKA_VERSION=master
 
 before_install:
-  - if [[ $TRAVIS_OS_NAME == linux ]]; then wget -qO - https://packages.confluent.io/deb/5.4/archive.key | sudo apt-key add - ; fi
+  - if [[ $TRAVIS_OS_NAME == linux ]]; then wget -qO - https://packages.confluent.io/deb/5.5/archive.key | sudo apt-key add - ; fi
   - if [[ $TRAVIS_OS_NAME == linux ]]; then sudo add-apt-repository "deb [arch=amd64] https://packages.confluent.io/deb/5.4 stable main" -y ; fi
   - if [[ $TRAVIS_OS_NAME == linux ]]; then sudo apt-get update -q ; fi
   - if [[ $TRAVIS_OS_NAME == linux ]]; then sudo apt-get install confluent-librdkafka-plugins -y ; fi