Revert "Fix DelegateClass block "method redefined" warning"

[nobu]

Reverts #13

We consider it is not worth to create intermediate modules always since the case overriding a method using super would be relatively rare.

The case can be achieved as the following by inheriting explicitly:

Overridden = Class.new(DelegateClass(Base)) do
  def foo
    super + "!"
  end
end