Added Python 3 support

I've added Python 3 support for the setup_tools setup files, which automatically can convert the code with 2to3 to Python 3 code.

Because of the changes in Python 3, the string arguments for the Telnetlib had to be converted to bytes, which was not automatically done by 2to3. As far as I could see (and tested for both 2 and 3) only the Telnetlib needed to access these bytes and I've changed this in the syntax in server.py.