Chat API #1
Description
Currently, Gab chat is based on an initial HTML page and a WebSocket connection for getting new posts to the currently viewed chat.
It really should be based off of an API, like the rest of Mastodon.
GET chat/:id should return a list of ChatMessage instances (JSON), controlled by the standard max_id, min_id, since_id, and limit parameters.
Fill this in more once we have source code.