Remove capybara-webkit and only use poltergeist
Update gems
Use poltergeist and Ruby 2.1.2. Don't use xvfb.
Use POST _method: 'PATCH' so AJAX works in poltergiest
Use OS tmp dir, not Rails tmp dir for data downlods
Run all acceptance tests with different drivers
Make downloads work across all browser test drivers. Use hacky AJAX call for poltergiest and capybara-webkit.