feat: Add new GPT-4-Vision Support and support custom URL with port.

[Kan1aSorata]

Hi, I'm a chinese student, thank for ur amazing repo about open-ai, It helps me a lot during develop. I add some new feature for this. Since our school uses its own OPENAI KEY platform, it is necessary to access it through a specific port, but i found this repo is not support that, so i add it, and also support the new GPT4-Vision.