Transitioning "width"property while DOM is changing

Question

I'd like to have a transition on width of a container which width of the container is equal to the width of content and content is changing by dom.

Here is a link http://jsfiddle.net/sabbasi/5xc5s08w/3/

Code from Fiddle:

var container = $(".container");
var nav = $(".nav");
var menu = $(".menu");

$(".sth1").click(function(){
    nav.detach();
    menu.appendTo(container);
    menu.show();
});

$("button").click(function(){
    menu.detach();
    nav.appendTo(container);
});