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
Fixed issue where cancelled operations aren't removed from runningOperations
Create NSOperation when start operation.
Method getDiskCount returns NSUInteger.
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
Adds -[SDWebImageManager saveImageToCache:forURL:] method
fix duplicate symbols when using with webp via pods
Merge pull request #646 from Whirlwind/master

add category for imageView's highlighted state
Update projects to recommended settings
Improve logging and fix arm64 warnings when printing integers with %d
Merge pull request #720 from rivera-ernesto/update_projects

Update projects to Xcode recommended settings
Merge pull request #721 from rivera-ernesto/improve_logging

Improve logging and fix arm64 warnings when printing integers with %d
fix UIImageView+HighlightedWebCache call error method
It's generally a bad idea to remove items from a container while iterating through it. And fix the thread safe issue.
Merge pull request #727 from kejinlu/master

It's generally a bad idea to remove items from a container while iterating through it.
The ioQueue is "SERIAL" ，so "dispatch_barrier_async" is not needed.