[w3c/webauthn] 1db4a9: allow u2f attestation to be chained

  Branch: refs/heads/acz
  Home:   https://github.com/w3c/webauthn
  Commit: 1db4a971289347ac41b724138f920d675726d19d
      https://github.com/w3c/webauthn/commit/1db4a971289347ac41b724138f920d675726d19d
  Author: Alexei Czeskis <aczeskis@google.com>
  Date:   2017-02-14 (Tue, 14 Feb 2017)

  Changed paths:
    M index.bs

  Log Message:
  -----------
  allow u2f attestation to be chained