Upgrade capybara to version 2.4.1

- Upgrade capybara because the old version puts a newline at the beginning of text submitted from a text area.
- Make changes to step definitions and specs because v2.4.1 handles css and xpath expectations differently.
- Correct text of title pages in custom error page feature - previous version of capybara was ignoring second argument of has_selector if the first argument was not a symbol.