HttpOutput does not respect http_proxy environment variable

[gravaton]

When attempting to use HttpOutput to push messages to an endpoint outside our corporate network, it attempts to connect directly. Go's documentation implies that the http_proxy environment variable should be respected however it does not seem to be. The Nagios Output plugin seems to have some capability for proxying but the HttpOutput plugin does not.

[michaelgibson]

I think....this would be as simple as adding Proxy: http.ProxyFromEnvironment,
From:
https://github.com/mozilla-services/heka/blob/dev/plugins/nagios/nagios_output.go#L94
To:
https://github.com/mozilla-services/heka/blob/dev/plugins/http/http_output.go#L81

But haven't tested it.