joinTo should filter out templates based on a regex or callable function

It doesn't seem that the regex/callable in the joinTo clause works properly. E.g.
```
templates: {
    joinTo: {
        'templates-app.js': /^app/,
        'templates-common.js': /^common/,
        'templates-admin.js': function(path) {
            return /^admin/.test(path);
        }
    }
}
```

This seems to work as far as filtering out the correct tpl.html files to include, but the top angular.module that gets prepended to the file includes **every** module, not just the filtered modules.

I'm new to brunch so I don't know if there's a simpler patch, but this seems to work for me.