This commit adds a unix socket on which you can receive internal events
as they happen. Currently the only supported event is a chat message
being added. Intended for external applications that depend on chat
messages, e.g. text-to-speech or Twitch Plays Pokémon.
Incoming requests are handled in anonstream/routes/. Route handlers
mainly depend on files in anonstream/, which in turn depend on files in
anonstream/helpers/ and anonstream/utils/. Utils are pure functions and
helpers are almost pure functions; they don't mutate state but they
do depend on the global app config.