Add Redis support for multi-server scaling

Currently room state is stored in memory. This means it only works with one server.

Add Redis adapter support so quick-socket works across multiple servers.

**What needs to be done:**
- Integrate socket.io-redis adapter
- Optional config in quickSocket.init()
- Update README with Redis usage

**Example:**
```javascript
quickSocket.init(server, { redis: { host: 'localhost', port: 6379 } })
```