Remove guard clause for new behaviour in ruby 2.0
Remove guard clause for new behaviour in ruby 2.0

* The new behaviour of ruby 2.0 seems that protected methods will return false
  for #respond_to? even if the method can be called directly since the caller is
  another instance of the same class. Change the library to use a different kind
  of test on the object, so rather than duck-typing, test that the other object
  is a Gateway and extract the relation and adapter when possible.

dkubb/axiom-do-adapter