How do I capitalise the Log Out function in the menu bar?

Hi guys,

I followed the very helpful code in this article to place a log in/log out link in the menu bar. I'm not too familiar with the code to capitalise the word in the menu though. the rest of our menu bar is capitalised and I would also like to capitalise the login/logout section.

I'm sure it's a simple case of adding more code to the functions.php file. Could you help please? The site is here:

Many thanks