Allow Travis build for different Node.js versions.

.travis.yml

@@ -1,6 +1,7 @@
 language: node_js
 
 node_js:
+  - '6'
   - '8.9'
 
 dist: trusty

packages/hapi-auth-udaru/test/test-server.js

@@ -1,9 +1,18 @@
 const config = require('../lib/config')()
 const Action = config.get('AuthConfig.Action')
 const Hapi = require('hapi')
+const chalk = require('chalk')
 
 let server = null
 
+let nodeVersion = process.versions.node.split('.')
+nodeVersion.pop() // We don't care about minor
+
+if (parseFloat(nodeVersion.join('.')) < 8.9) {
+  console.log(chalk.yellow('hapi-auth-udaru requires Node.js greater than 8.9.0. Exiting without errors.'))
+  process.exit(0)
+}
+
 module.exports = async function () {
   if (server) return server