Make it more reusable, by:
- Renaming `attachment/update` to `attachment/edit`
- Refactoring the CSS styles into their own stylesheet
- Allow to specify the 'accept' option
Capybara's `have_select` can be very slow for elemtns with many options
(see https://github.com/teamcapybara/capybara/issues/1527)
This is because Capybara asserts that no other elements than the
required ones are selected.
This faster version is not as complete, but helps when checking the
countries list or the years in a date picker.
