The script you are refering is only css.
If you wish to use those styles, I believe there is no need to implemenent the css style sheet like I previously suggested.
To implement your custom style, simply copy the code and wrap it within the
<style> tag like so:
/* paste your css code below this line */
Also, it looks like pace need to be reffered as soon as possible to detect the loading progress.
<link href="/pace/themes/pace-theme-barber-shop.css" rel="stylesheet" />
or if you wish to use custom css:
/* pate your css code below this line */
replace the /pace/pace.js respectively /pace/themes/pace-theme-barber-shop.css by one of the CDN full path provided here
Hope that helps