Drop supporting iOS4 to use weak references.
Convert the project to the settings recommended by Xcode5.
Convert project settings and code to ARC by the refactoring function of Xcode.
Remove unnecessary @synthesize in the app delete of the sample app.
Migrate to the modern Objective-C.
Merge branch 'support-arc'
Fix the issue that the observer of ‘enabled’ property is not removed if the same instance of EEToolbarCenterButtonItem is passed to EEToolbarCenterButtonOverlay.
Add shouldAutorotate and supportedInterfaceOrientations methods to the sample view controller for iOS6 or later.
Add Default-568@2x.png to support 4-inch retina screen in the sample app.
Update README.md to inform the supported environment and the usage with ARC.
Merge branch 'update-sample-project'