I ran into issue 2 while trying to convert a large project from AMD/requirejs format to commonjs/browserify. This quirk means that I can't make use of relations in my models without defining my app first (so that the `require()` function exists), but defining my app first fails since it doesn't have access to Spine and other libraries, which I concat into a separate file.

Even if I could define my bundles first, I'd have a similar problem if I used multiple browserify bundles and lazy-loaded some of them later: Spine would grab the original version of `require()`, but since each browserify bundle [wraps any previous `require()` it finds](https://github.com/substack/browser-pack/blob/master/prelude.js) and replaces the global variable, Spine wouldn't have access to the modules in subsequently-loaded bundles.

Anyway, I realize this problem is somewhat specific to the way browserify does things, but it seems to be the foremost method of using commonjs in the browser (if you've eschewed Hem), and I think the cost of looking up the right function on demand is small. While looking at how to fix it, I noticed issue 1, and figured it was also an opportunity to disambiguate the use of two possibly-different `require()` functions.