Tick marks are back for revisions

* Simple tick marks
* Tooltips snap to tick marks
* Tooltips arrow reverses side for LTR/RTL
* Fix for routing issue where just the hash is changed in the URL bar relating to compare two mode

see #24425. props adamsilverstein, ocean90.

git-svn-id: https://core.svn.wordpress.org/trunk@24595 1a063a9b-81f0-0310-95a4-ce76da25c4cd