feat(tooltip): Update tooltip placement after height changes

The tooltip was not correctly updating it's placement (see issue #1109) after dom elements were inserted above it because it was only checking placement when the tooltip was original placed.  I can think of lots of scenarios where this would cause issues (rotating variable height content above, ajax results displayed above, form validation helpers above).

I added a listener using setInterval and ran tests to make sure all still pass.  Issue is corrected.

I am happy to write test but how do I know in my test if the positioning is changing when dom elements change?  How can I add dom elements and check style properties?