JPG etc are not scaled properly - Fix

[NielsLust]

The Lightbox code only checks if the extension of the image is in lowercase.

Solution:

Change
if(s.match(/\.(jpeg|jpg|gif|png)$/)!=null)

Into:
if(s.match(/\.(jpeg|JPEG|jpg|JPG|gif|GIF|png|PNG)$/)!=null)

Solution found here: http://stackoverflow.com/questions/19961569/nivo-lightbox-adding-tags-to-image-to-make-them-iframes

Can someone please add this as pull request? Thanks!