v0.8.0

Better support for long-lived connections:

• Add support for sending responses using request.accept() and request.send().
• That is now the recommended way to do chunked responses.
• This also provides support for long polling and SSE.
• Also add RequestSet, request.sleep_while_connected() and request.wakeup() for long polling and SSE.
• Websocket requests have a somewhat cleaner API.

Improved asset handler:

• Fix that HEAD requests on the asset handler util included the body in the response.
• Dont send compressed assets if compression does not help, and never compress videos.
• Fix/improve cache control header.

Further:

• Implement ASGI 3.0.
• More tests (full coverage for ws now too).
• Improved docs.