Correcting #respond_to? method arity

Both of the following methods had method arity of 1:

* Rails::Railtie::Configuration#respond_to?
* ActionDispatch::Response#respond_to?

Other instances of #respond_to? in Rails have a method arity of -2.
The method arity of -2 matches the interface for Ruby 1.9.3, 2.0.0,
2.1.2, and 2.1.0.

See:
http://ruby-doc.org/core-2.1.0/Object.html#method-i-respond_to-3F
http://ruby-doc.org/core-2.1.2/Object.html#method-i-respond_to-3F
http://ruby-doc.org/core-2.0.0/Object.html#method-i-respond_to-3F
http://ruby-doc.org/core-1.9.3/Object.html#method-i-respond_to-3F

Closes rails/rails#16685
Merge pull request #16686 from jeremyf/normalizing-respond-to-method-definitions

Correcting #respond_to? method arity