[w3c/webauthn] 317861: Add U2F attestation format

  Branch: refs/heads/vgb-u2f-attestation
  Home:   https://github.com/w3c/webauthn
  Commit: 317861f6d932bbdd533be0e802f62117c165eab4
      https://github.com/w3c/webauthn/commit/317861f6d932bbdd533be0e802f62117c165eab4
  Author: Vijay Bharadwaj <vijaybh@users.noreply.github.com>
  Date:   2017-01-11 (Wed, 11 Jan 2017)

  Changed paths:
    M index.bs

  Log Message:
  -----------
  Add U2F attestation format

Fixes #214