tweak .travis.yml

.travis.yml

@@ -1,6 +1,10 @@
 language: node_js
 node_js:
   - "8"
+dist: trusty   # needed for chrome headless
+sudo: required # needed for chrome headless
+addons:
+  chrome: stable
 services:
   - postgresql
   - redis-server
@@ -8,7 +12,11 @@ before_install:
   - rvm install 2.5.0
 before_script:
   - npm run lint
-script: travis_retry npm test
+script: npm run test-browser
+env:
+  matrix:
+  - BROWSER=chrome:headless
+  - BROWSER=firefox:headless
 branches:
   only:
   - master