Update CI config to use Trusty image
Update CI config to use Trusty image

Update the Travis image to make it possible to build Node modules; see
https://docs.travis-ci.com/user/languages/javascript-with-nodejs#Node.js-v4-(or-io.js-v3)-compiler-requirements

GoogleChromeLabs/gulliver,GoogleChromeLabs/gulliver,GoogleChromeLabs/gulliver