message: improve yarn output in travis log
diff: @@ -45,7 +45,7 @@ before_install:
  - echo $JAVA_HOME
  install:
  - - yarn install
  + - yarn install --non-interactive
  - wget https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-${ES_VERSION}.tar.gz
  - tar -xzf elasticsearch-${ES_VERSION}.tar.gz
  - ./elasticsearch-${ES_VERSION}/bin/elasticsearch 2>&1 >> /dev/null &
  