Click on disabled tab still shows corresponding pane

Created by: Paladinium

Using the tab JavaScript plugin with alpha v2, a disabled tab switches the tab content when being clicked. This bug can be seen in the documentation:

• Go to http://v4-alpha.getbootstrap.com/components/navs/#javascript-behavior
• Add class 'disabled' to the 'Profile' tab (e.g. using Firebug)
• Notice that the 'Profile' tab correctly appears to be visually disabled, also when hovering over the tab
• Click on the 'Profile' tab
• The tab's content is switched

Expected: no tab switch happens when clicking on disabled tabs.

The JavaScript needs to take the 'disabled' CSS class (maybe also the 'disabled' attribute) on nav-link into account.