[w3c/webauthn] 989f52: Adding u2f appid extension

  Branch: refs/heads/acz
  Home:   https://github.com/w3c/webauthn
  Commit: 989f52ea5390ec7d41e28bd3b0bebb4396b3e967
      https://github.com/w3c/webauthn/commit/989f52ea5390ec7d41e28bd3b0bebb4396b3e967
  Author: Alexei Czeskis <aczeskis@google.com>
  Date:   2016-10-04 (Tue, 04 Oct 2016)

  Changed paths:
    M index.bs

  Log Message:
  -----------
  Adding u2f appid extension

Closes Issue #216