unsupported type for static module: VariableDeclarator

when running `browserify js/pre-bro.app.js` using brfs, I receive the following error:

```
Error: unsupported type for static module: VariableDeclarator
at expression:

fs
while parsing file: /Users/me/dev/git/studio-module-media/js/pre-bro.app.js
at traverse (/Users/me/dev/git/studio-module-media/node_modules/brfs/node_modules/static-module/index.js:285:25)
```

I have determined that the lines from the source file that trigger this error are the following:

```
...
// Generated by CoffeeScript 1.8.0
(function() {
var $, Definition, Marionette, QuickPublishView, Studio, Template, fs, _;

$ = require('jquery');

_ = require('underscore');

fs = require('fs');
....
```

I'm having trouble figuring out what's going on