Connection/Client rework

[stkfd]

This reworks the way connections and clients are handled. Currently still a rough work in progress, at the end there should be three public ways to connect to chat through this library:

1. Only create a connection with no extra logic like rate limit detection, auto-reconnects, middleware etc. Pretty much just IRC + Twitch extensions parsing around a websocket connection
2. Creating a client which internally handles a single connection, but comes "batteries included", so it handles rate limit detection, reconnect requests from twitch, detects broken network connections (indicated by IO errors or by getting no response to ping messages to Twitch) and handles other typical requirements. The client keeps track of which channels it should be in and on reconnect automatically rejoins. This is probably the most common use case.
3. A connection pool, very similar to the above client but with multiple connections. The public interface would probably set a threshold of maximum channels per connection, and the pool internally adds or removes connections as required.

Once finished this will address #6 and #7.