chore: set up Sauce Labs with Travis

This should not affect the Jenkins build at all.

Now, the Travis build uses Chrome on Sauce Labs, which in theory gives us opportunity to use any
browser/platform that Sauce Labs offers.

karma-docs.conf.js

@@ -33,4 +33,6 @@ module.exports = function(config) {
       suite: 'Docs'
     }
   });
+
+  config.sauceLabs.testName = 'AngularJS: docs';
 };