Stacking submenu items

For issue #3.

Changed the JS back to toggle the menu on mousedown (for now, anyway).

Added a function to stack submenu items behind a parent item based on
the parent's position in the stack and the id attribute which the parent
and children must share.

Modified the function which expanded the entire menu to expand elements
without the child class.

Added some class and id information to the HTML so the JS/jQuery could
hook in.

The submenu doesn't expand, yet, but that's next up on the list.

This commit does not close issue #3