Adjusts documentation to accommodate -[UIViewController automaticallyAdjustsScrollViewInsets] + typo

Use of `-[UIViewController automaticallyAdjustsScrollViewInsets]` breaks SSPullToRefresh.

This is because UIKit does the automatic `contentInset` adjustment *after* `viewDidLoad`. Instead, the inset adjustment is integrated into the `viewWillLayoutSubviews`/`viewDidLayoutSubviews` API flow.

The solution I came up with is to use `viewDidLayoutSubviews` to instantiate an `SSPullToRefreshView`, when using `automaticallyAdjustsScrollViewInsets`.

Also, minor typo. :)