[71755478] specs for js on frontend

- use `poltergeist` as capybara driver for `phantomjs`
- specs for tabs JS and popups
- tell `VCR` to ignore *localhost* requests (`poltergeist` uses a random local port to talk to `phantomjs`)
[71755478] set `default_url_options`

so that specs don't complain about this
Merge pull request #134 from bitzesty/71755478-js-specs

[71755478] specs for js on frontend