Removed old info about ARC from README.

Closes #136
Fixed problem with delegate method in demo.

Closes #137
Updated README
Improved demo project.
Added showPreviousPhotoAnimated: and showNextPhotoAnimated: methods.

As discussed in #135
Fixed mutation while enumerating exception.

Closes #139 and closes #138
Fixed bug when swiping to navigate photos that are zoomed to fill.
Improved loadUnderlyingImageAndNotify
Added ability to select photos.