Abitlity to sort assets within a bundle

Hi, I realize you've been working on require.js support, but I also like how Sprockets in the Rails asset pipeline is able to combine js files while taking dependencies into account by looking for a ("//= require <dep.js>") directive in the js file.  It's a bit simpler if all you need is the ability to break your js into a file hierarchy and specify dependencies between files.

I implemented this for a small project of mine, and I thought I should share in case you're interested in incorporating it into your own branch.  It just adds a new extension point in the bundle code, and the rest is implemented as a sort extension.

Thanks