Containerize travis builds. (#897)

Author: aweingarten

scripts/travis/.travis.yml

@@ -1,5 +1,5 @@
 # Note that the example .travis.yml file for child projects lives in /install.
-sudo: required
+sudo: false
 language: php
 dist: trusty
 
@@ -25,6 +25,9 @@ cache:
 addons:
   ssh_known_hosts:
   # - svn-4786.devcloud.hosting.acquia.com
+  apt:
+    sources:
+    - xvfb
 
 # @see https://docs.travis-ci.com/user/notifications
 notifications:
@@ -56,7 +59,6 @@ install:
   # Initialize drupal console default configuration.
   - drupal init
   # Initialize xvfb (see https://docs.travis-ci.com/user/gui-and-headless-browsers)
-  - sudo apt-get install xvfb
   - export DISPLAY=:99.0
   - sh -e /etc/init.d/xvfb start
   # Installs chromedriver to vendor/bin.