Add websocket support to tinybrain

[Terkwood]

This change set allows the katago wrapper to connect to a remote websocket in BUGOUT's cloud deployment, and respond to katago queries.

Advances #67.

• Use a header for basic authorization
• Deal with PASS command in Katago (see KataGoImpl TODO)
• Finish websocket client
• Finish katago loop
• Set up a dummy robocall service which can emit game states
• clean up TODOs
• honor board size

Passing

In the GTP spec:

A vertex is a board coordinate consisting of one letter and one number, as defined in section 2.11, or the string pass''. Vertices are not case sensitive. Examples: B13'', ``j11''.

[Terkwood]

Another decent-looking ws lib :

• https://github.com/snapview/tungstenite-rs/blob/master/examples/server.rs
• https://github.com/snapview/tungstenite-rs/blob/master/examples/client.rs