Replace PIL (Python Imaging Library) with Pillow.
Updated CHANGELOG.
Merge branch 'pillow'
Make Photo.date_added editable.

date_added should be editable because it's what the sorting inside
a gallery is based on and there's no other means of adjusting the 
order of photos inside a gallery yet.
Merge pull request #41 from jnns/patch-1

Make Photo.date_added editable.