Initial Profobuf messages

[doomspork]

A starting point for our conversation on leveraging Protobuf messages in our events.

[doomspork]

In the interest of not going hogwild with CI/CD — yet — we're going to need to manually generate the Elixir files when updating the Protobuf files.

[doomspork]

We should also discuss whether or not we want to wrap all of our messages in an "Envelope" that contains meta data we might want (timestamps, source, et al).

[btkostner]

mhmmm, we should at least create a mix task / alias to run that command. Are we able to override the built in mix compile command to also run that command or would that be horrible / impossible?

[btkostner]

Also, if we are generating elixir in this repo, why not just have elixir code without the protobuf stuff? If we are planning to use this across languages, we should make this repo just the protobuf stuff and do all of the elixir stuff in what ever project uses this.

[btkostner]