v2.1.1

New features

• Added -trusted-downstreams flag (TRUSTED_DOWNSTREAMS env var) for trusting
  X-Forwarded-* headers from certain clients (useful when Centauri is behind
  another proxy).

Other changes

• Reverted changes to write and idle timeouts from 2.0.1. These were
  interfering with upstream services that expect clients to stay connected
  for a long time (e.g. long polling).