Fix for Ticket #2531339

[muffinresearch]

Fix bug in Cache for when uniqueKeys = true, remove the existing item from the cache rather than shift.

[ericf]

@muffinresearch Could you please [digitally] sign the YUI CLA? http://yuilibrary.com/contribute/cla/

Thanks!

What Is the Purpose of the CLA?

The CLA ensures that everyone who submits a work of authorship to the YUI Library is contributing work that is their own or for which they can authoritatively speak. This protects the tens of thousands of developers who use YUI in their daily work, all of whom rely on YUI's BSD license to appropriately cover their use of the library.

The CLA does not transfer title or copyright of your contributed work to Yahoo!. It merely guarantees that you approve the use of your work within YUI and by those who use the library under the terms of its license.

[muffinresearch]

@ericf - hi, I signed the CLA literally a couple of hours ago :)

[ericf]

Oh cool, thanks!

[ericf]

I'm going to punt on this until 3.6.0 when I'll be working on the Cache utility.