[w3c/webauthn] 62b67c: Cleaned up exposition of processing rules (#154)

  Branch: refs/heads/master
  Home:   https://github.com/w3c/webauthn
  Commit: 62b67c02a37ab54ca8b3c1f7606bb7351298ddec
      https://github.com/w3c/webauthn/commit/62b67c02a37ab54ca8b3c1f7606bb7351298ddec
  Author: Vijay Bharadwaj <vijaybh@users.noreply.github.com>
  Date:   2016-08-31 (Wed, 31 Aug 2016)

  Changed paths:
    M index.bs

  Log Message:
  -----------
  Cleaned up exposition of processing rules (#154)

* Replace facet with origin

Facet was a holdover from the old FIDO specs and origin is the term used
everywhere in this spec (as well as in recent FIDO specs)

* Clean up explanation of computing clientDataHash and passing to authenticator

Fixes #153

* Remove text from authnsel extension to avoid chicken-and-egg problem

Fixes #152

* Address comments from @equalsJeffH