Created group folder for splash images.
Reduced file size of splash images with "ImageOptim".
AspectFillThumbFetcher now caches images as jpg files.

Allows much greater control over file size of bundled images as they can now be pngcrush'ed or otherwise iptimized. I optimized the bundled images included with this commit using "ImageOptim" resulting in a smaller app binary.
Merge pull request #108 from montehurd/optimizeImages

Reduced app binary size by optimizing bundled images.