Not pass empty kwargs to ActionPack

Empty kwargs occur in simple calls without any parameters or headers, e.g. `get '/some/path`. Code added in rails#58 passes empty kwargs in the form of an empty hash to  ActionPack that considers it not to be compatible with the new kwargs-style syntax and emits useless a deprecation warning.

Author: mingan

lib/rails/controller/testing/integration.rb

@@ -13,7 +13,11 @@ module Integration
         http_verbs.each do |method|
           define_method(method) do |*args, **kwargs|
             reset_template_assertion
-            super(*args, **kwargs)
+            if kwargs == {}
+              super(*args)
+            else
+              super(*args, **kwargs)
+            end
           end
         end
       end