NEW FEATURE: added video and audio to SHKTumblr
REFACTORING: canShareItem
NEW FEATURE: file type share now remembers favourites for each mime type
NEW FEATURE: file share example now shows how to share different file types
NEW FEATURE: SHKTumblr URL share now accepts and properly displays SHKURLShareTypeAudio, Video, Image and Webpage
REFACTORING: removed addSkipBackupAttributeToItemAtURL: calls and NSFileManager category

it was used to exclude items saved for offline queue from backup. It is not needed, because offline queue is in CACHE directory, which is not included in backups by default.
REFACTORING: improved SHKItem saving + SHKOfflineSharer uses modern objective-c syntax
REFACTORING: SHKFacebook now uses ShareKit's new builtin routines for saving/restoring the item