added support for a custom asset selection view
added missing files for the custom cell feature and example
added build.gradle file
Added podspec
Added info about unit testing to README
Moved resources into resource bundle, fixed loading and unit tests
Cleanup project after new resource bundle target
added prefix for static lib
set lib und bundle deployment target to 6.0
Fixed podspec for resource bundle use
Fixed image loading in OBDefaultAssetCollectionViewCell