Change gulp test to use Chrome

PhantomJS appears not to support the full XHR2 spec. Test pass in
Chrome but in PhantomJS they with DOM Exception 12 on the line where
axios sets `XHR.responseType`

Author: clayreimann

karma.conf.js

@@ -15,9 +15,9 @@ module.exports = function(config) {
 
       autoWatch: false,
 
-      frameworks: ['mocha', 'chai'],
+      frameworks: ['mocha', 'chai', 'phantomjs-shim'],
 
-      browsers: ['PhantomJS'],
+      browsers: ['Chrome'],
 
       coverageReporter: {
          reporters: [