fix #96
new arrow style
remove observer 'contentSize'
resolve pullToRefreshView position error if the network request is less than start animation time.
resolve pullToRefreshView position error if the network request is less than start animation time.
Merge branch 'fix' of github.com:foxling/SVPullToRefresh
tweak
Merge branch 'master' of https://github.com/foxling/SVPullToRefresh