fix a crash bug, crash when removing observors

change deployment target to iOS 8.0

minor bug fix, fix bug, trigger pull to refresh can't trigger to call handler

minor api change

move useless message in control

Merge branch 'master' of https://github.com/IamAlchemist/SVPullToRefresh

add the share scheme for carthage

Create README.md

add infinite scrolling view

temp submit

minor change in example

the first simple version

minor change

add the bottom pull to refresh view in example

minor change