Please add simple.modbus to pypi source distfile

[0-wiz-0]

When packaging for pkgsrc, we use the pypi source distfiles. When running the tests, two fail because simple.modbus is not part of the file. Can you please add it? Thanks.

[favalex]

This should do #34

If it works for your purposes I will close the ticket.

[0-wiz-0]

Thank you! I can tell you when a make a new pypi distfile :-) but if you prefer we can close it in the meantime.