Use transactional fixtures

spec/features/campaign_requests_spec.rb:16 fails intermittently.
I suspect this is dependent on the order on which the test cases
are run. Transactional fixtures should fix this by making sure
each test case runs in isolation.

spec/rails_helper.rb

@@ -23,6 +23,7 @@
 Dir[Rails.root.join("spec/support/**/*.rb")].each { |f| require f }
 
 RSpec.configure do |config|
+  config.use_transactional_fixtures = true
   # RSpec Rails can automatically mix in different behaviours to your tests
   # based on their file location, for example enabling you to call `get` and
   # `post` in specs under `spec/controllers`.