Rewrite Tooltip-placement.html, removing unnecessary dependency on dijit.form.ValidationTextBox etc.    Calling dijit.Tooltip.show() should be sufficient for testing tooltip placement, and will hopefully have less intermittent failures than the old test.   Refs #4282 !strict.

git-svn-id: http://svn.dojotoolkit.org/src/dijit/trunk@26937 560b804f-0ae3-0310-86f3-f6aa0a117693