Avoid rewriting tab panel content.
Allow 'label' to accept a Y.Node instance (brings inline with 'content')
Add tests for Y.Node instance label/content and event clobbering.
Add label/content getter tests.
Allow label to be handled via the getter rather than parsing from html.
Include HTML when testing label value from existing markup.
Merge branch 'dev-master' into tab-events
Merge branch 'tab-events' into dev-master