chore: install Chrome-related dependencies in Travis CI

.travis.yml

@@ -1 +1,20 @@
 language: node_js
+
+sudo: required
+dist: trusty
+addons:
+  apt:
+    sources:
+      - google-chrome
+    packages:
+      - google-chrome-stable
+
+before_install:
+    # setting the path for phantom.js 2.0.0
+    - export PATH=/usr/local/phantomjs-2.0.0/bin:$PATH
+    # starting a GUI to run tests, per
+    # https://docs.travis-ci.com/user/gui-and-headless-browsers/#Using-xvfb-to-Run-Tests-That-Require-a-GUI
+    - export DISPLAY=:99.0
+    - sh -e /etc/init.d/xvfb start
+    - "npm config set spin false"
+    - "npm install -g npm@^2"