[Twisted-Python] Twisted cred perspective unicode support

[Brian Warner]

> The patch should probably be reverted. The perspective name etc. should
> always be a string because the storage you use for it may have no notion
> of unicode. If you want to use unicode there they should just be UTF-8ed
> anyway.

*nod*. I've just reverted it. Sorry RodrigoB, look to itamar's suggestions
for some possibilities.

thanks,
 -Brian