Bump capybara from 2.12.1 to 2.15.1
Bump capybara from 2.12.1 to 2.15.1

Bumps [capybara](https://github.com/teamcapybara/capybara) from 2.12.1 to 2.15.1.
- [Changelog](https://github.com/teamcapybara/capybara/blob/master/History.md)
- [Commits](https://github.com/teamcapybara/capybara/compare/2.12.1...2.15.1)
rdunlop/unicycling-rulebook,rdunlop/unicycling-rulebook,rdunlop/unicycling-rulebook,rdunlop/unicycling-rulebook