Got a little farther. Handshake seems to work now.

Separated out the crt and key files, changed up some of the config dictionaries based on a github search.

dispatch_config = build_dispatch_config()
{ :ok, _ } = :cowboy.start_tls(:api,
                                100,
                               [port: 8443,
                                keyfile: "/home/crunch/server.key",
                                certfile: "/home/crunch/server.crt"],
                               %{ env: %{dispatch: dispatch_config}}
                               )

Unforunately still fails when I try to send anything over the websocket connection.