Cache clientHeight, fix lag when tooltip tracks cursor. Closes GH-1
Refactor move() into create()
Try precreating tooltip nodes, but it is ridiculously slows because of the clientHeight calculation

Ref GH-1
Revert "Try precreating tooltip nodes, but it is ridiculously slows because of the clientHeight calculation"

Ref GH-1

This reverts commit 8487dcac68bc0d054c79adc978b48ac62bccfee5.
Cache string-only tooltip height, fix lag on creating most new tooltips. Improves GH-1
Change to listen on mouseenter/leave instead of mouseover/out (no bubbling)
Precreate tooltip nodes again
Recognize text nodes (Text) as DOM elements
Accept DOM nodes as second argument to constructor, as a shortcut, just like text or array (instead of full opts dictionary)
Update demo