Merge pull request #252 from reidmain/master

decodedImageWithImage: ignores scale and orientation
Fix an LLVM warning (fix #254)
Fix Xcode 4.6 warnings
isRunning method added at SDWebImageManager
Change SDWebImageManager to use shared image cache
Merge pull request #264 from aburgel/use_shared_cache

Change SDWebImageManager to use shared image cache
Do not mark URLs a fail when error is due to missing network connection
Don't dispatch cancelAll calls. 

- should fix pre-fetcher problems #247
- cancelAll should be always called using the main thread
Merge pull request #268 from matej/prefetcher-fix

Don't dispatch cancelAll calls. 
Merge pull request #260 from kawanet/master

isRunning method added at SDWebImageManager
Add imageFromMemoryCacheForKey: method to synchronously query the memory cache (fix #263)
Fix podspec (fix #253)
Fixed bug where NSInvalidArgumentException was thrown if an image with a nil URL was downloaded.