Add failing test to expose bug in -[UIScrollView scrollViewToVisible:animated:].
Fix bug in [UIScrollView scrollViewToVisible:animated:] that improperly
set UIScrollView's contentOffset when the accessibility element is not
fully onscreen.
Increases specificity of setOn:... to expect a button, since it is the default trait and it reduces failured on diplicates.
Defined the `_touchesEvent` selector for the compiler.

Resolves #285 and #289.
Merge pull request #312 from talko/scrollviewfix

Failing test and fix for bug in [UIScrollView scrollViewToVisible:animated:]