ARC support

[ronnyandre]

When trying to build, Xcode gives me an error in ImageManager.m saying 'retain' is unavaiable: not available in automatic reference counting mode

[Julioacarrettoni]

My image manager is NOT ARC compatible :(
I need to do something like this
http://blog.mugunthkumar.com/articles/migrating-your-code-to-objective-c-arc/
In order to make it ARC compatible.​