[w3c/webauthn] c85f7a: Incorporate feedback from JeffH, part 2

  Branch: refs/heads/vgb-refine-makecredential
  Home:   https://github.com/w3c/webauthn
  Commit: c85f7a881e43cdf20d4d0d20cb23a2b47192516c
      https://github.com/w3c/webauthn/commit/c85f7a881e43cdf20d4d0d20cb23a2b47192516c
  Author: Vijay Bharadwaj <vijaybh@users.noreply.github.com>
  Date:   2017-03-02 (Thu, 02 Mar 2017)

  Changed paths:
    M index.bs

  Log Message:
  -----------
  Incorporate feedback from JeffH, part 2

Use "client data" and "authenticator data" instead of "ClientData" and
"authenticatorData".