Fix feature spec

[essa]

This fixes the broken feature spec, spec/features/paypal_spec.rb.

I found this spec fails and was skipped on other stable branches. I need to customize this gem for our site so I fixed the specs.

Following changes were needed to run it against current PayPal site.

1. Versionfile was needed to generate a test app by rake test_app
2. Need to specify version of rake
3. I Changed many queries for HTML elements to match the current PayPal site
4. I inserted many sleeps for waiting PayPal client side scripts to be ready

Here's difficult or mysterious parts for adjusting test script for PayPal site.

• The new login form is inside of an iframe although there are hidden input fields of email and password outside of it
• Most of event handlers take some seconds after visual elements appear on browser, so I need to insert sleep for waiting it
• With geckodriver, cookies are reused so login page of PayPal will be skipped when we run many tests at once.

I think this is used for master or other stable branches but I made a PR for 1-3-stable which I'm using now.