Support configuring HTTP / HTTPS proxy

[yutayamate]

Hi Domo team,

I found current version of the SDK does not have support for configuring HTTP / HTTP proxy, which is necessary for communicating with the API from enterprise networks where outbound traffic to the Internet is ristricted.

I've tried adding new parameters (proxies and verify) to do this. It would be great if your team could review this PR. Thank you!

from pydomo import Domo

proxies = {'https': 'http://someproxy:8080'}
ssl_verify = False

domo = Domo(client_id='*****', client_secret='*****', proxies=proxies, verify=ssl_verify)