Change core extension's asSingleton to asSharedInstance.
Fix tip plugin bug where with _onTriggerMouseMove.

bindAll was being called too early, it seems,
based on instances get constructed by
CoffeeScript.
Fixup 2970b56: fix _bindTrigger so supplying a tip trigger works.
Remove zombie tip-snapping logic.
Minor code cleanup.
Harden tip plugin's _moveToTrigger...

First use position (relative) instead of offset
(absolute) to support any context.

Second, detect with isTriggerOnly and refine
offsets, which have changed with the cursorHeight
updates in 0b487a4.