response: rename `transport` to `writer`.

Not the same thing.
http.headers: parse pre-decoded lines. Add a status line parser.
Add an incomplete parser of HTTP requests.
Use custom Protocol logic.
Synchronize WebSocket writes.
Remove aiohttp from dependencies.
Fix Protocol.error.
Read request payloads.
Pass only the StreamReader into `http`, not the whole `Protocol`.
Headers: require `-`, do not convert `_` into `-`.
Dispose of asyncio servers properly.
Use a coroutine instead of a StreamWhateverProtocol.
Fix the bootstrap example.
Improve the way responses are written.