Reposition the modal on size changed.

I'm not sure whether I've missed some of your features.
Now I'm trying to do my own auto reposition, hope it may be useful.

1. Initial modal (with collapsed part) .
![bootstrap-modal-reposition-01](https://f.cloud.github.com/assets/822889/144302/be5991ec-7407-11e2-92c4-cb3ddbb615bb.png)

2. Default modal. When expand the collapsed part, the modal is overflown without reposition (the browser window is also overflown).
![bootstrap-modal-reposition-03](https://f.cloud.github.com/assets/822889/144307/23572bd6-7408-11e2-9a4b-0f133472ab59.png)

3. Modal with '.modal-reposition'. When expand the collapsed part, now the modal is fitted into the browser window with no outer overflow.
![bootstrap-modal-reposition-02](https://f.cloud.github.com/assets/822889/144318/938e76ac-7408-11e2-89ab-8d9e8273e962.png)