add AuthorizedSession

[runawaycoast]

This pr adds a new way to set ApiConfig and making requests.

• ApiConfig Previously, we use ApiConfig as a global singleton to set api_key and configuration, users cannot use different configurations within a single python executable. In this pr, we will allow users to pass an instance of ApiConfig into request api.

    import nasdaqdatalink
    api_config = nasdaqdatalink.ApiConfig()
    api_config.verify_ssl = False
    api_config.api_key = 'somekey'
    data = nasdaqdatalink.get('table/abc', start_date='2022-05-10', end_date='2022-05-10', api_config=api_config)

• AuthorizedSession We introduced a new interface in this pr which allow users to making multiple requests within a single session to remove the overhead of creating session every times.

    from nasdaqdatalink
    api_config = nasdaqdatalink.ApiConfig()
    api_config.verify_ssl = False
    authed_session = nasdaqdatalink.AuthorizedSession(api_config)
    data = authed_session.get('table/abc', start_date='2022-05-10', end_date='2022-05-10')