Add files immediately prior to those in ./app

Previously, when requiring files, they were appended to `app.files`. With this change, requiring files will have them precede the app's files.

This works for multiple requires, the first requires get first priority.

This was brought up in:
https://groups.google.com/d/msg/rubymotion/WxXBx6lXx0E/9KZmpZ6Cyv0J

I haven't tested this, but it seems like a good default behavior.