Capping Rails version

Our code seems to error when running against Rails 3.2.14.

```
    ActiveRecord::ConfigurationError:
       Association named 'provider' was not found on Provider; perhaps you misspelled it?
     # ./app/models/authorization/product.rb:22:in `block (2 levels) in <module:Product>'
     # ./app/models/authorization/repository.rb:43:in `content_readable'
     # ./app/models/authorization/repository.rb:36:in `libraries_content_readable'
     # ./app/controllers/content_search_controller.rb:577:in `process_repos'
     # ./app/controllers/content_search_controller.rb:100:in `packages'
     # ./app/lib/util/thread_session.rb:104:in `thread_locals'
     # ./spec/controllers/content_search_controller_spec.rb:81:in `block (6 levels) in <top (required)>'
```