Allow setting a custom memory cost limit for the in-memory NSCache. This can help to keep memory down before memory warnings are sent by the device.
NSInteger -> NSUInteger, add getter method
Merge pull request #556 from JoshuaGross/master

Allow setting a custom memory cost limit for the in-memory NSCache.
up version 3.5 in podspec to be consistent with latest
Merge pull request #558 from shifu/master

up version 3.5 in podspec to be consistent with latest
Add HTTP header filter to pick headers for downloading request
Merge pull request #514 from crazytonyli/header-picking

Add HTTP header passing test to pick header for downloading request
added currentDownload Count, to allow someone to see how many operations are left.
matched coding conventions
Merge pull request #562 from mknippen/master

added currentDownload Count, to allow someone to see how many operations are left.
Bump version to 3.5.1 (fix #568)
Added a delegate for the web image prefetched.
Code cleanup.
Merge pull request #577 from pieterclaerhout/master

Added a delegate for the web image prefetched.
Merge branch 'master' of https://github.com/rs/SDWebImage into barz-master