fileio.py contains some documentation errors

[eclrbohnhoff]

The doc in fileio.py says this: https://github.com/gmggroup/omf/blob/bd28cd65c9eaae7e71988a4b8abcf2f918c792c6/omf/fileio.py#L33

But actually uses this: https://github.com/gmggroup/omf/blob/bd28cd65c9eaae7e71988a4b8abcf2f918c792c6/omf/fileio.py#L73

The doc says the header uses a UUID in little-endian: https://github.com/gmggroup/omf/blob/bd28cd65c9eaae7e71988a4b8abcf2f918c792c6/omf/fileio.py#L35

But actually uses big-endian: https://github.com/gmggroup/omf/blob/bd28cd65c9eaae7e71988a4b8abcf2f918c792c6/omf/fileio.py#L77

As described by python doc: https://docs.python.org/3/library/uuid.html

UUID.bytes
The UUID as a 16-byte string (containing the six integer fields in big-endian byte order).