It's not obvious what "the way" to teardown window event handlers is in
Ember. The datacenter-picker is permanently in the app during usage, but
in tests I'm assuming it gets added and removed lots.

So when you run the tests, as the tests aren't run in an isolated runner
the QUnit test runner ends up with a click handler on it, So if you
click on the test runner one of the tests will fail.

The failure is related to there not being an element with a `.contains`
method. So this checks that the element is truthy first, i.e. it exists.
If it doesn't it just bails out.

Go with `rsync` over `cp` for putting the api double into public for the
moment

`rect.top` is zero until the tab panel becomes visible, resize will need
to be called when the tab is clicked also

Tables need to calculate their sizing depending on other things in the
DOM. When a table is in a tab panel, some of these things aren't visible
and therefore some values are zero during `didInsertElement`.

This commit ensures that the resize calc of the table is performed when
it's parent tab is clicked (and therefore when the table 'appears')

WIP: Ideally all of these would go