RSpec testing: Added new Gemfile group "javascript_testing" so that users can
easily choose not to install capybara-webkit by using the "--without
javascript_testing" option to 'bundle install'.

Changed spec_helper.rb to add in this group (unless RAILS_DEBUG=true, in which
case the debug group is used instead).
Bulk Upload: Ensure wizard pages aren't accessible when they shouldn't be to
ensure well-defined progression through the wizard (RM #2525).

Added some missing return statements after redirects.
Bulk Upload: In "store_file", simply move the uploaded Tempfile instead of
reading its contents and writing it out again.

In bulk upload tests, close the on-the-fly fixture files that are to be uploaded
after writing them; we were getting intermittent failures having to do with
files having no content when we didn't do this.