AUI-1362 - Make aui-tabview accessible

Hi Marc,

Another update for https://issues.liferay.com/browse/AUI-1362.

I BROKE EVERYTHING.

jk.  I think this is really close.  It works almost exactly the same as http://heydonworks.com/practical_aria_examples/#tab-interface.

The only difference is, say if you keep hitting the left arrow, it will wrap instead of stopping.  I thought this made more sense and was simpler logic.

I made some comments on 5188987 explaining some changes I made that might look weird.

Please let me know what you think.

Thanks!