[ADD] Adding the ability to use a proxy to receive requests.

[themanyfaceddemon]

This PR adds the ability to specify a proxy for requests. I'm not sure about some parts of the code, but I hope everything will be stable.

[Strvm]

Hi! First off, thank you for your contribution. Overall your PR looks pretty good, I just went ahead and made some small changes:

• Instead of querying google to test the proxy, I changed it to be https://api.ipify.org/?format=json which is a bit more lightweight.
• Instead of raising an Exception when we fail to use the proxy, now raise a ConnectionError.
• If the proxy does work, update the Session so always use the proxy by self.session.proxies = self.proxy
• Made the authenticating to FB also use the proxy when set.

Thank you!

[themanyfaceddemon]

Thanks for the clarification, I just haven’t worked with requests very much.