Silence Warning Regarding Use of Splat

I was seeing the following in my console:

```
/home/vagrant/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/devise-3.2.4/app/controllers/devise_controller.rb:9: warning: `*' interpreted as argument prefix
/home/vagrant/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/devise-3.2.4/app/controllers/devise_controller.rb:10: warning: `*' interpreted as argument prefix
```

This change silences this warning.