possibility to add proxy

Hi,
thanks for the useful library. However, I need to configure a proxy. Is it possible to update the library and to allow this? I think there are some changes needed in api.py:
`
proxy= {"https": "..."}
requests.get("...", proxies=proxy, auth=("...", "..."))
`

Same for put, post, delete. 

Thanks,
Meinhard

