sonnyparlin/PullToRefresh — pull request #2 by drewish (2012-07-14 23:26:40+00:00)
Title: Hold the reference to scrollView until we remove our observer

I was running into a similar problem to the one described here:
https://github.com/sonnyparlin/PullToRefresh/issues/1
It seemed cleaner to switch to a strong reference so the scrollView
sticks around until we're done with it then we can let it deallocate.