python2 support for pyhermes

[Lagovas]

PyArg_ParseTupleAndKeywords doesn't support y# format in python2 (https://docs.python.org/2/c-api/arg.html) so I replaced it with s# that works on python2/3

Py_BuildValue doesn't support y# too and s# format will not work on python3 because it will try convert raw bytes to utf-8, so I replaced it with PyBytes usage that works on python2/3 (https://docs.python.org/3/howto/cporting.html#str-unicode-unification)

plus replaced PyObject_CallMethod with PyObject_CallMethodObjArgs which takes PyObject from PyBytes and works similarly on py2/3

[vixentael]

I'll check on MacOS later

[vixentael]

I checked, everything is good.

thank you @Lagovas