Added an option to save the cookie file to be used with cURL

[MuntashirAkon]

Added an optional argument curl_cookie_file to CloudFlareScraper.get_tokens() in order to export the two cf cookies in a file that can be directly used with cURL.

[Anorov]

The cf_clearance cookie is fairly short-lived. I don't think there's a need for this. Saving the cookies to disk for curl to repeatedly use will just lead to problems once cf_clearance expires.

[MuntashirAkon]

It's okay if you think this modification is irrelevant. In my case where the automation system involves multiple programming languages, this modification is a general necessity. Also, however short lived the cookie is it's a bad idea to generate them every time you make a request to the server (it's fairly time consuming). Of course, the user of this tool should already know that this cookie is short lived. Otherwise, they would've used tools like pycookiecheat to get the cookies straight from the Chromium browsers.

[Anorov]

That's reasonable. I'll reopen this but I'd like to reimplement it myself with a different API.

[MuntashirAkon]

OK.