Use NSCache instead of a dictionary for the memory cache.
Updated gitignore to include build
add further explanation for Build Settings info
Merge pull request #174 from jianlin/master

add explanation of where to find the link flag and the header search paths
add instructions on how to pop out the box for header search paths
quote the string to add

for the search paths
HeaderFile.h confusing

users may copy and paste it to source code (HeaderFile.h)
more readable
Merge pull request #175 from jianlin/master

add instructions
needed to quote the <Multiple values>
Merge pull request #176 from jianlin/master

needed to quote <Multiple values>
Add some security around wrongly typed URL argument
Non ARC fix
Add the ability to set max cache age.
Add and update podspec
Merge pull request #149 from acoomans/master

Added build directory to gitignore
Add a cached parameter to the success block to tell the receiver if the image came from cache or network #181
Update podspec for 2.7
Remove alpha channel (may break some PNG/GIF with alpha, pull request welcome)
Add ImageIO dep