context isn't lost when URL is aliasing

Thanks for this theme. It's awesomely flexible!

This simple patch allows creating context (active tab on the primary navigation) just by URL aliasing the menus.

Example:
example.com/views -> the tab “Views” is active with the css id=current-xx set on the li tag
example.com/views/add -> the tab “Views” is still active. This url is an alias for node/add/views

introfini