Update to rails 5

[wwahammy]

• Perform Rails 5 gem update
• Update bin/bundle
• Update config/environment.rb
• Update config/spring.rb
• Add config/initializers/application_controller_renderer.rb
• Add config/initializers/new_framework_defaults.rb
• Update bin/rails
• Move session_store into an initializer
• Update config/environment.rb
• Update bin/setup
• Update config/environment/development.rb
• Move some config into config/initializers/carrierwave.rb
• Move some session_store config into config/initializers/session_store.rb
• Add bin/update

NOTE: DO NOT discuss internal CommitChange information in your PR; this PR will be public.
Link back to the issue in the Tix repo when you need to do that.