- Don't use `sleep` (most of the time was wasted by that)
- Expect some elements to be visible instead: capybara is smart enough
  to retry a few times if it cannot find an element
- See
  https://github.com/teamcapybara/capybara#asynchronous-javascript-ajax-and-friends
- Don't create unneccessary DB records
- Group some examples together to shave some setup time (where it makes
  sense)
Signed-off-by: NRémy Coutable <remy@rymai.me>