[core] Fix responds_to test helper.

As per discussion on #305.

Also clean up output for parser test.

tests/core/parser_tests.rb

@@ -59,7 +59,7 @@ posuere eu odio. Donec sodales, ante porta condimentum
   }
 
 
-  tests('TestParser').returns(@response) do
+  tests('TestParser').returns(@response, "returns the response") do
     test_parser = TestParser.new
     Nokogiri::XML::SAX::Parser.new(test_parser).parse(@xml)
     test_parser.response

tests/helpers/responds_to_helper.rb

@@ -3,11 +3,11 @@ module Shindo
 
     def responds_to(method_names)
       for method_name in [*method_names]
-        tests("#respond_to?(:#{method_name})").succeeds do
+        tests("#respond_to?(:#{method_name})").returns(true) do
           @instance.respond_to?(method_name)
         end
       end
     end
 
   end
-end
+end