outputLabel does not render tabindex

A minor issue was discovered where outputLabel failed to render tabindex even though it's part of the VDL docs: https://docs.oracle.com/javaee/7/javaserver-faces-2-2/vdldocs-facelets/h/outputLabel.html

However, note that  tabindex is rendered for inputText.

<h:outputLabel tabindex="1" value="your name" />
<h:inputText tabindex="2" />
 

The other attributes seemed to have rendered fine from what I tested ( style, title, onclick.. etc)

I have a fix for this, and will get a PR up soon.

It seems like a check for tabindex was never added, so the fix adds it in.