StringIO does not respond to to_io
ruby 1.9.3p385 (2013-02-06 revision 39114) [x86_64-linux]
In my project, I'm using "object.respond_to? :to_io" to check if the object is IO-ish.
(I heard that this is the preferred way to do that some time ago.)
However, StringIO does not seem to define to_io. Is this intended?