Fix name of "six.moves.StringIO".

[ericvsmith]

The correct name is StringIO, not CStringIO.

[ericvsmith]

I don't think this one character change needs a CLA.

[regebro]

Thanks for this!

I was surprised about this, and checked. And in fact, both works. The documentation only mentions cStringIO, though, which is strange. And there of course is just six.StringIO, which has the benefit of dealing with both bytes and unicode, so that should also be mentioned, really.

I need to add a few more words about this, I think.

[ericvsmith]

I was surprised, too.

And looking back through my command history, it's because I typo'd "cStringIO" as "CStringIO". I'm an idiot. Sorry for the noise. I would have sworn I copy and pasted that text from the web page, but I guess I didn't.

I apologize for wasting your time.

[regebro]

Nono, all good, this clearly needs updating, even if it isn't a bug. I'll leave it open as a reminder.