As well as `<select multiple="multiple" ...>`, it's also valid to use an empty attribute (i.e. `<select multiple ... >`). In order to support this, we need to treat `multiple` in the same way as `disabled` or `checked`.
Timeouts can be set using browser.timeout = <seconds>. When a command or page load takes longer the specified timeout a Capybara::TimeoutError will be raised. Calls to reset! will reset the timeout. You can also clear the timeout by setting it to -1. The timeout is implemented as a Command decorator.