Update capybara

<del>Just getting early feedback from Travis to see if the failures match with the ones I have locally.</del>

* [x] Fix all failures
* [x] Use `find(sel, match: :first)` over `first(sel)`
* [x] Eliminate all sleeps
* [x] Use `execute_script` over `evaluate_script`

In a long term refactor we also should get rid of all `visible: false`s I introduce in this PR and replace as many `execute_script`s with calls to Capybara as possible.