used bytestrings where appropriate

27 tests passed now
fixed some encoding problems

all tests in test_encoding pass now (28 passed)
used bytestrings where appropriate

needed to introduce a unicode version of FOLD called uFOLD
some internal cleanup seems to be needed, not everything uses unicode
just yet
used bytestrings where appropriate

only in test_icalendar.py
don't yet know why one foldline test should raise an exception
used bytestrings where appropriate

again
added TODO for python3