[w3c/webauthn] a9c6b3: Remove rpId from ClientData

  Branch: refs/heads/vgb-explicit-rpid
  Home:   https://github.com/w3c/webauthn
  Commit: a9c6b38eaf4936c01981e4f7918a73542f833847
      https://github.com/w3c/webauthn/commit/a9c6b38eaf4936c01981e4f7918a73542f833847
  Author: Vijay Bharadwaj <vijaybh@users.noreply.github.com>
  Date:   2016-09-16 (Fri, 16 Sep 2016)

  Changed paths:
    M index.bs

  Log Message:
  -----------
  Remove rpId from ClientData

Since rpId is now equal to origin except when explicitly specified by
the caller, and it is folded into the authenticatorData, having it in
ClientData adds no value.

Fixes #189