Text::CSV::Encoded::Coder::EncodeGuess dies on utf-8 data

Hello!

::EncodeGuess now dies on utf8 input due to the recent Text::CSV auto-utf8 changes.  This patch avoids double-decoding by skipping it when the encoder is guessed to be utf8 and the automatic_UTF8 flag is set.  I've also added a test to 05_guess.t.

Thank you for your work on this module and have a great day!

Cheers,
Fitz

-- commit message below --

* Recent versions of Text::CSV_{XS,PP} now automatically decode utf-8
   strings.  ::EncodeGuess wasn't paying attention to this and
   attempting to doubly-decode utf-8 strings, causing the fatal error:
   "Cannot decode string with wide character".  This patch skips the
   decode when the utf8 encoder is guessed and the automatic_UTF8 flag
   is set.

 * add utf8 test to t/tests/05_guess.t