Update Travis node version.
Update Travis node version.

vogdb/pulsar-rest-api,njam/pulsar-rest-api,cargomedia/pulsar-rest-api,cargomedia/pulsar-rest-api,njam/pulsar-rest-api,cargomedia/pulsar-rest-api,vogdb/pulsar-rest-api,njam/pulsar-rest-api,vogdb/pulsar-rest-api,njam/pulsar-rest-api,cargomedia/pulsar-rest-api