How to make my navigation bar scale up when resizing browser window

Does anyone know how can I make my navigation bar scale up like this when I resize my window? (look at this website below to see how the navigation menu scales up when you resize your browser window. This is what I want to make).

http://www.templatemonster.com/demo/52266.html

I have posted my code to jsfiddle. Please find the link to my second comment below.