Add support for billy's selenium drivers

[y-yagi]

#109 supported billy, but only added poltergeist driver. This patch supports more drivers(related with selenium).

Ref: https://github.com/oesmith/puffing-billy/blob/fc12d19cfa27182463c5c300acacd517a557d339/lib/billy/browsers/capybara.rb#L48-L96