An flask application factory, as explained here:
    http://flask.pocoo.org/docs/patterns/appfactories/

    Arguments:
        object_name: the python path of the config object,
                     e.g. webapp.settings.ProdConfig

        env: The name of the current environment, e.g. prod or dev

def create_app(object_name):
    """
    An flask application factory, as explained here:
    http://flask.pocoo.org/docs/patterns/appfactories/

    Arguments:
        object_name: the python path of the config object,
                     e.g. webapp.settings.ProdConfig

        env: The name of the current environment, e.g. prod or dev
    """
    app = Flask(__name__)

    app.config.from_object(object_name)

    # initialize the cache
    cache.init_app(app)

    # initialize the debug tool bar
    debug_toolbar.init_app(app)

    # initialize SQLAlchemy
    db.init_app(app)

    return app