Fix the truncate() semantics -- it should not affect the current position.
Switch wave.py/chunk.py to struct.unpack_from() to support bytes.
Don't use writelines() on binary files (test_fileinput.py).
write() returns the number of bytes/characters written/buffered.
FileIO.close() calls self.flush().
Implement readinto() for buffered readers.
Tests th check all these.
Test proper behavior of __enter__/__exit__.