Improved User Agent emulation

[msjonker]

This applies techniques from https://github.com/VeNoMouS/cloudscraper to more closely mimic requests from a browser, so there is a better chance of not being detected as a bot to have to deal with a captcha in the first place. In my testing, these changes created identical requests to cloudscraper, allowing me to access pages that were previously protected with a captcha.

Summary of changes:

• Capitalized header names. While the specification is that case doesn't matter, Chrome and Firefox seem to send them capitalized.
• Ordered headers. "Host" needs to be the first header.
• Uses the headers of the user-agent. Headers used are from https://raw.githubusercontent.com/VeNoMouS/cloudscraper/master/cloudscraper/user_agent/browsers.json
• Uses the ciphers and cipher ordering of the user agent. Also taken from https://raw.githubusercontent.com/VeNoMouS/cloudscraper/master/cloudscraper/user_agent/browsers.json
• Various other SSL settings that are needed to generate "Client Hello" packets identical to those of cloudscraper.

For my purposes, I needed to be able to scrape https://bouqs.com/, but without these changes, I was blocked by a challenge. After these changes, requests go through with no challenge. I'm not terribly familiar with the Cloudflare firewall, but I know they compute a "Bot Threat Score" and I think these changes help to lower it enough that, at least in my case, it allows my requests through.