[push-api] Clean up push service terminology. (#114)

* Prefer "push service" over "push server", "push system" or "system" to align with protocol spec
* Simplify and cleanup diagram, remove unnecessary push client

issue #113 
issue #80 
You can view, comment on, or merge this pull request online at:

  https://github.com/w3c/push-api/pull/114

-- Commit Summary --

  * Clean up push service terminology.

-- File Changes --

    M index.html (93)
    M sequence_diagram.png (0)

-- Patch Links --

https://github.com/w3c/push-api/pull/114.patch
https://github.com/w3c/push-api/pull/114.diff

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/push-api/pull/114