Fixed issue with contentBox being left in Y.Node._instances, when deep destroying an un-rendered Widget

The contentBox was left in the Node cache:

1. If using the deep destroy option [`widget.destroy(true)`] and,
2. If the widget was **not** rendered.

In this scenario, the contentBox wouldn't sit under the boundingBox, so boundingBox.empty() didn't have any childNodes to destroy.

For the rendered case, boundingBox.empty() would take care of the contentBox just fine. Also for the non-deep scenario, we'd remove(true) both boxes independently.

Testing
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All library tests, including the one added for this issue pass:
✔ [Total]: Passed: 10861 Failed: 0 Total: 10956 (ignored 95)

Confirmed that the newly added test failed prior to the fix.

Reviewing
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The pull request also cleans up trailing whitespace and long lines to keep jshint happy, while we're building widget.

The only commit with functional changes is: https://github.com/sdesai/yui3/commit/8858aa9f23621064cd3b5d065468a9650638e124