add menu-item to docs / support for active css class

[mbeckenbach]

Please add the menu-item from the docs page (https://material.angularjs.org) to docs.
Very helpfull component.

Also please add support for a simple active state css class instead of md-highlight so you can simply set active highlighting via ui-sref-active from ui-router.

[epelc]

@mbeckenbach Are you referring to the classes the sidenav is using?

If so you can rip them out quite easily if you need similar styles for your own app.

[marcysutton]

The docs sidenav is soon going to change to an Expand/Collapse list control (#985) to better match the Material Design spec. But we also have the menu component on the horizon. To achieve a similar effect to what you see in the docs currently, you could always nest buttons inside of list-items. The functionality for this should already exist...you would just have to wire up the expand/collapse.