Log Message:
Update ruby-rspec-rails to 2.13.0.

### 2.13.0 / 2013-02-23
[full changelog](http://github.com/rspec/rspec-rails/compare/v2.12.2...v2.13.0)

Enhancements

* `be_valid` matcher includes validation error messages. (Tom Scott)
* Adds cucumber scenario showing how to invoke an anonymous controller's
  non-resourceful actions. (Paulo Luis Franchini Casaretto)
* Null template handler is used when views are stubbed. (Daniel Schierbeck)
* The generated `spec_helper.rb` in Rails 4 includes a check for pending
  migrations. (Andy Lindeman)
* Adds `rake spec:features` task. (itzki)
* Rake tasks are automatically generated for each spec/ directory.
  (Rudolf Schmidt)