documented workaround for frameworks that extend optional libraries
Added method to SDWebImageManager to check if an image exists in either the disk OR the memory cache
add category for imageView's highlighted state
Updates progress callback to use NSInteger

Pull Request #606 resolves this issue in the code but not in the Documentation.
Merge pull request #685 from jeffleeismyhero/patch-1

Updates progress callback to use NSInteger
Create NSOperation when start operation.
Method getDiskCount returns NSUInteger.
Merge branch 'master' of https://github.com/rs/SDWebImage
Port Max's crash fix to my 3.6 fork
Merge pull request #694 from shifu/master

Port Max's crash fix to my 3.6 fork
Update SDWebImageDownloaderOperation.m

Fixing race condition that causes cancellation of one download operation to stop a run loop that is now used for another download operation. Race is introduced through -performSelector:onThread:withObject:waitUntilDone:
Merge branch 'master' of https://github.com/rs/SDWebImage
Merge pull request #698 from salling/master

Fixing race in SDWebImageDownloaderOperation leading to erroneous timeout.
Save image in cache before calling completion block
Merge pull request #700 from herrernst/master

Save image in cache before calling completion block
Overload -setImageWithURL to delay setting of placeholder image until after loading
Moved the delay placeholder flag to SDWebImageOptions
Updated bitwise operator to correctly find option if more than 1 are included
Wrapped placeholder check in parens to work with bitwise
Merge branch 'master' of https://github.com/rs/SDWebImage
Adds -[SDWebImageManager saveImageToCache:forURL:] method