Supprot HTTP proxy for SignalFX.ingest()

[RayYou]

Hi,

I am using signalfx-lambda to emit the metrics for my aws lambda functions. It works great on public network, but I need to use http proxy to route the requests on VPC. I didn't see any option to enable http proxy yet.

signalfx-lambda rely on SignalFx.ingest to create the event injest client, and I found that there is a similar change Pull 79 made for signalflow. Could you implement the http proxy for injest() as well ?

Thanks!