[test] transform modules in karma so sinon can stub properly

 - require karma tests
 - temporarily turn off module transformation on airbnb-preset

.travis.yml

@@ -34,6 +34,3 @@ matrix:
       env: COVERAGE=true TEST=false
     - node_js: "lts/*"
       env: KARMA=true TEST=false
-  allow_failures:
-    - node_js: "9"
-    - env: KARMA=true TEST=false # temporary

karma.conf.js

@@ -33,8 +33,13 @@ module.exports = (config) => {
               path.join(__dirname, 'test'),
               require.resolve('airbnb-js-shims'),
             ],
-            query: {
-              presets: ['airbnb'],
+            options: {
+              presets: [
+                // setting modules to false so it does not transform twice
+                ['airbnb', { modules: false }],
+                // transform to cjs so sinon can stub properly
+                ['@babel/preset-env', { modules: 'cjs' }],
+              ],
             },
           },