SavReaderNp should return unicode chars in when ioUtf8=True

[Albert-Jan Roskam]

.. because that's consistent with SavReader.

The dtype should be U (capital-u), not S.

with SavReader("greetings.sav", ioUtf8=True) as reader:
    records = reader.all()  # list of namedtuples
assert isinstance(records[0[.greeting, unicode).

with SavReaderNp("greetings.sav", ioUtf8=True) as reader:
    records = reader.all()  # recarray
assert isinstance(records.greeting[0], unicode).