iOS：ODRefreshControl

https://github.com/Sephiroth87/ODRefreshControl

Important note if your project doesn’t use ARC: you must add the -fobjc-arc compiler flag toODRefreshControl.m in Target Settings > Build Phases > Compile Sources.

ODRefreshControl is a “pull down to refresh” control for UIScrollView, like the one Apple introduced in iOS6, but available to anyone from iOS4 and up.