soften the lightbox overlay

This *soften* the lightbox overlay to

![screen shot 2013-06-26 at 2 29 12 am](https://f.cloud.github.com/assets/362783/706696/73737b16-ddf7-11e2-9bc5-a56cd12f506a.png)

**NOTE**: this *deactivate* the previous overlay and the new one will only appear for (newly/re) baked posts.