Proxy supports proxies

The sampling proxy previously ignored HTTPS proxies that might be configured via the environment. This version now honors the HTTPS_PROXY environment variable to send traffic to Honeycomb via an outbound proxy.

Documentation, logging, bug fixes

This change

• updates some documentation on how to run samproxy.
• adds some debug logs clarifying the flow of spans and traces through the system to help an operator verify (in test conditions) that the cluster is functioning correctly
• fixes a bug in the sharding code to correctly send spans to peer shards

Adding in redis cluster management

This version adds command line flags and an environment variable to enable using Redis to manage members of the samproxy cluster.

CI tweaks

No change to samproxy, just changing build configs.

Additional packaging formats

Adding .deb and .rpm to the artifacts generated as part of a release.

Initial versioned release

This is the first release of samproxy to have an artifact published back to github with a fixed version.

Changes since the last "release" (aka head of master before this version) is the addition of the option to use Redis to handle managing the list of online peers within the samproxy cluster.

This release is still beta; expect more to come.