Also ran gofmt on everything. Thanks again @paralin. #334

Co-authored-by: Christian Stewart <christian@paral.in>

Closes #247

HTTP header values, as opposed to header keys,
are case sensitive, but implementation of headerTokens()
before this patch would return lowered values always.

This old behavior could lead to chromium (v87) WebSocket
rejecting connnection because negotiated subprotocol,
returned in Sec-WebSocket-Protocol header (lowered
be headerToken() function) would not match one sent
by client, in case client specified value with capital
letters.

Closes #220 and #230

Closes #194

Closes #189

See https://github.com/nhooyr/websocket/issues/182

Closes #182

Closes #179

math/rand was being used inappropiately and did not have
a init function for every file it was used in.

Removes the tiny filenames polluting the root directory.

Closes #121

The boys in the office hated it.

Highly unfortunate but makes sense as it seems confusing.

Will be cleaner in GitHub as the README.md is the first
thing you will see instead of a massive directory listing.

Closes #122

Also simplified and refactored the Conn tests.

More changes soon.

Closes #39