Fix behavior on when using responders on destroy operation

After #destroy AR returns the object with #destroyed? true, frozen but *true*
so responders consider as a valid object and redirect to model_path(@model.id)

If it was destroyed, we pass the model instead of operation, and it returns
correctly to models_path
Add #persisted? method to operation

Its no good controller access the model, so added #persisted? to operation
this way controller dont need to access model to work with respond_with
in a destroy action
add test/rails to test Responder.
add rake rails for rails tests.
add tests for #respond.
remove unneeded files.
Merge branch 'fix_respond_to_with_destroy_operation' of https://github.com/fernandes/trailblazer
test Responder destroy semantics.