Support for sending erros from behind proxy

[doonetheprune]

I cannot see in the documentation or in the code any options to configure sentry for working behind a proxy. Whenever I send an error I get.

raven@1.2.1 alert: failed to send exception to sentry: connect ECONNREFUSED 108.168.254.122:443

[doonetheprune]

Bump

[amitkverma]

This might help
https://docs.sentry.io/server/nginx/