chore(tests): use headless browser for tests

.travis.yml

@@ -1,6 +1,6 @@
 language: node_js
 node_js:
-  - "5.9"
+  - "6.13"
 env:
   global:
     - CXX=g++-4.8

karma.conf.js

@@ -1,3 +1,5 @@
+process.env.CHROME_BIN = require('puppeteer').executablePath();
+
 module.exports = function(config) {
   config.set({
 
@@ -40,7 +42,7 @@ module.exports = function(config) {
     // - Safari (only Mac)
     // - PhantomJS
     // - IE (only Windows)
-    browsers: [process.env.TRAVIS ? 'Firefox' : 'Chrome'],
+    browsers: [process.env.TRAVIS ? 'Firefox' : 'ChromeHeadless'],
 
     // Continuous Integration mode
     // if true, it capture browsers, run tests and exit

package.json

@@ -39,12 +39,13 @@
     "jshint": "^2.9.1",
     "jshint-stylish": "~0.3.0",
     "karma": "^0.12.16",
-    "karma-chrome-launcher": "^0.1.3",
+    "karma-chrome-launcher": "^2.2.0",
     "karma-coverage": "~0.2",
     "karma-firefox-launcher": "~1.0",
     "karma-jasmine": "~0.2",
     "karma-ng-html2js-preprocessor": "^0.1.0",
     "karma-phantomjs-launcher": "~0.1.4",
+    "puppeteer": "^1.0.0",
     "run-sequence": "^1.1.5",
     "streamqueue": "^1.1.1",
     "title-case": "^1.1.2"