update virtualenv python code example

Example 1: python virtual environment

python3 -m venv env
python -m virtualenv env #py2

source env/bin/activate

#all this is on same directory

Example 2: create a venv

# Create the virtual environment.
python -m venv venv

# Activate the env.
venv\Scripts\activate.bat

Example 3: venv upgrade python

python3 -m venv --upgrade ENV_DIR

Example 4: venv

python -m venv c:\path\to\myenv

Example 5: virtual environment python

python3 -m venv tutorial-env