Get specs running under rails 4.2.0.beta-1

The 4.2.0.beta-1 specs are failing because the released version rails-deprecated_sanitizer gem includes Rails::Railtie.  This is fixed (https://github.com/rails/rails-deprecated_sanitizer/pull/1) but not planned for release.  

This change uses the github version of rails-deprecated_sanitizer for 4.2.0.beta1

There is one failing test under 4.2.0.beta-1 when this is merged in.