Update ETModel to Rails 4.1

Other changes related to the upgrade:

  * Fixed translations on the "save scenario" form (perhaps broken by a newer version of simple_form?).
  * Fixed "toggle" links in the admin section, broken by the removal of "link_to_function" in Rails 4.0.
  * Remove xray-rails.
  * Updated RSpec, FactoryGirl.
  * I18n-JS updated to 3.0.0.rc5 (was 2.1.2).
  * JBuilder updated to 2.0.6 (was 1.5.2).