Run npm nodejs job with Firefox browser

This patch update browser from Chrome to Firefox
in karma.conf.js because nodejs fails with Chrome
browser as not able to access some URL.
So let's switch to Firefox browser now then we can
use Chrome browser in future once this issue is resolved.

Change-Id: I33b911143208fb63548d776cbf3dc4249d4e3394

karma.conf.js

@@ -98,7 +98,7 @@ module.exports = function(config) {
 
     // start these browsers
     // available browser launchers: https://npmjs.org/browse/keyword/karma-launcher
-    browsers: ['Chrome', ],
+    browsers: ['Firefox', ],
 
 
     // Continuous Integration mode

package.json

@@ -30,9 +30,8 @@
     "js-yaml": "3.8.1",
     "json2yaml": "1.1.0",
     "karma": "1.7.1",
-    "karma-chrome-launcher": "2.2.0",
     "karma-coverage": "1.1.1",
-    "karma-firefox-launcher": "1.0.1",
+    "karma-firefox-launcher": "2.1.0",
     "karma-jasmine": "1.1.0",
     "karma-ng-html2js-preprocessor": "1.0.0",
     "vis": "4.3.0"