This file is no longer relevant and is there primarily for backwards
compatibility. See this post for sharing JS and CSS assets across
multiple applications:
http://joelmoss.info/switchboard/blog/2142:Whats_new_in_CakePHP_Asset_Sharing
All you really have to do is drop the files into vendors/js
I'm noticing that the vendors.php file refers to ..\..\vendors
\javascript\, however the folder doesn't exist or is still named
vendors\js\ in the cake templates. Is this intentional if I want to
use the vendors.php structure do I need to add a javascript folder to
vendors and then add my .js file