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.