httpx removed 'proxies' parameter

[Relax594]

In Version 0.26 of httpx the proxies parameter was deprecated.

Now in version 0.28 it got removed which breaks this package when being used with version 0.28+.

I've provided a pull request to fix this.
#160

Please consider and release a new updated version with it to provide compatibility with the latest httpx version

[Clasko]

Hi, any chance to merge this? :)