to_websocket fixes & adding filter value by set membership

FIXING WEBSOCKET TO WORK WITH CHROME:
it's really fun getting lost in labyrinthian RFC specs until you finally end up on the first page of RFC 2616 (HTTP 1.1) as a "reference"

This websocket handshake config (no config) works with Chrome. Even though the RFC for websockets says that the server can respond with one protocol specified by the client or a protocol not specified by the client (what...? whatever, this works).