add flask custom cmmmand to environmental variable code example

Example 1: run flask app from command line

# For bash do this:
set FLASK_APP=<app_name>

# For powershell do this:
$env FLASK_APP=<app_name>

# Run it like this
flask run

Example 2: flask commands

# manage.py

from flask_script import Manager

from myapp import app

manager = Manager(app)

@manager.command
def hello():
    print "hello"

if __name__ == "__main__":
    manager.run()