Added DNCollectionViewCell base to add workaround to Xcode6 nib bug

- Added DNCollectionViewCell base to add workaround to Xcode6 nib bug
- Updated podspec version

Signed-off-by: Darren Ehlers <me@darrenehlers.com>
Updated comment block

Signed-off-by: Darren Ehlers <me@darrenehlers.com>