Fix mouse resize in nested containers

Long description:

Currently, when resizing a container with mod+mouse (right click) and
the currently focused container is the first (clicking next to the
left/top border) or the last (right/bottom border) node in the queue,
resizing would fail. With this patch, i3 now searches for a parent
container with the desired orientation.

fixes #1084

To apply this patch, use:
curl http://cr.i3wm.org/patch/227/raw.patch | git am

@@ -46,7 +46,7 @@ static bool tiling_resize_for_border(Con *con, border_t border, xcb_button_press

         first = resize_con;

         second = (way == 'n') ? TAILQ_NEXT(first, nodes) : TAILQ_PREV(first, nodes_head, nodes);

         if (second == TAILQ_END(&(first->nodes_head))) {

-            second = NULL;

+            return tiling_resize_for_border(resize_con->parent, border, event);

         }

         else if (way == 'p') {

             Con *tmp = first;