[manifest] clarify display-mode and UAs and iframes (closes #309) (#318)

@kenchris, please take a look. 
You can view, comment on, or merge this pull request online at:

  https://github.com/w3c/manifest/pull/318

-- Commit Summary --

  * clarify display-mode and UAs and iframes (closes #309)

-- File Changes --

    M index.html (18)

-- Patch Links --

https://github.com/w3c/manifest/pull/318.patch
https://github.com/w3c/manifest/pull/318.diff

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/manifest/pull/318