Revisions: use `reject()`, not `fail()`, when rejecting a deferred.

See #24425.

git-svn-id: https://core.svn.wordpress.org/trunk@24666 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Revisions: Loading indicator, cleanup, bug fixes.

* Loading indicator when the user is waiting for a trip to the server.
* Bug fixes for diff priming.
* Fix the date display.
* Forget about local comparator, instead order by `modified` on the server.
* Initialize the frame model before the view (this was the source of a LOT of heartache).

git-svn-id: https://core.svn.wordpress.org/trunk@24667 1a063a9b-81f0-0310-95a4-ce76da25c4cd