Ability to override default oauth_* actions, like existing oauth_new

I think it would be helpfull to have an option to override all default controller not only auth#new.
For example I needed to return a js response after authorizing application instead of redirecting.
```ruby
def create
   super do
     respond_to do |format|
       format.html
       format.js do
         render :show
       end
     end
   end
end
```