use UIBezierPath instead of CGMutablePath
changes mainRadius and subRadius linearly
shortened threshold
use CAShapeLayer
use CAAnimation for shrinking animation
use CAAnimation for scaling animation
fixed bug on creating bezierPath
link QuartzCore with ISRfreshControlTests
Merge branch 'refactor/ISGumView' into develop
set deployment target 4.3 and removed storyboard
avoids setting default appearance if runtime is iOS4
modified scaling animation for iOS4
Merge branch 'feature/ios4' into develop
refactored ISRefreshControl
updated demoViewController
fixed bug caused by contentInset
changed fillMode of CAAnimations
universal demo app
will not call setNeedsLayout if visible contents is far away from refresh control #13
improved animation