Proxy detection mechanism only recognises uppercase environment variables

Hello!

Current implementation as in WebSocket._detect_proxies class method will only detect uppercase proxy server environment variables. This is sub-optimal, since majority of software respects lowercase http_proxy and https_proxy environment variables.

Luckily case insensitive functionality is already available in Python's standard library, specifically in urllib.request.getproxies https://docs.python.org/3/library/urllib.request.html?highlight=getproxies#urllib.request.getproxies.

Please, consider using urllib.request.getproxies() for proxy detection instead of custom solution!
Thanks!

[willmcgugan]

Thanks, I wasn't aware of geproxies in urllib. Looks like I'll need to implement a Python2.7 version, as it is Py3 only.

@willmcgugan Right, did not think about 2.7 compatibility. Well, Python 2.7 has urllib.proxies() https://docs.python.org/2.7/library/urllib.html?highlight=getproxies#urllib.getproxies

And I bet six can take care of that.