Revert ES6ification of end-to-end tests and add instructions for Windows

Because the tests are run directly by node, we have to use the CommonJS module syntax. We could run the thing through babel, but then we just have another babel.

Windows instructions are from experience and may not be optimized.

test/end-to-end-tests/src/logbuffer.js

@@ -15,7 +15,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-export default class LogBuffer {
+module.exports = class LogBuffer {
     constructor(page, eventName, eventMapper, reduceAsync=false, initialValue = "") {
         this.buffer = initialValue;
         page.on(eventName, (arg) => {