Remove standalone pytest run_tests.py bundle Newer pytest doesn't support generating stand alone testing bundles. Python 3.9 generates errors running the current run_tests.py. Changed doc to use pythonX -m pytest test/ and some light directions on how to install pytest. Thanks to jerrykan for recommendations on how to do the doc updates.

#!/usr/bin/env python

# Roundup requires Python 2.7+ as mentioned in doc\installation.txt
from __future__ import print_function
import sys

VERSION_NEEDED = (2, 7)

if sys.version_info < VERSION_NEEDED:
    print("Content-Type: text/plain\n")
    print("Roundup requires Python %s.%s or newer." % VERSION_NEEDED)
    sys.exit(0)