Remove aws-ses, we use smtp

and it is causing issues with resolving gem dependencies
when trying to update test gems.
Updated capybara, poltergeist, capybara-mechanize

need this to fix timing issues and get the
latest bug-fixes.
Make features work with latest capybara
Make tests work with latest capybara

capybara doesn't find disabled fields by default
and option `selected` for `has_select?` need to be
and `Array` or `String`.
Merge pull request #150 from alphagov/update-test-gems

Update test gems