Ensure the cursor visible in the suggestions view.

The original implementation did not care about scrollable suggestions view.
But I needed it so I made this patch.
This implementation does not cache properties so it has room to be impromved. :)
Merge branch 'feature/ensure-cursor-visible' of git://github.com/pokelabo/typeahead.js into integration-0.9.3
Modify #209 to work correctly with margins/paddings.
Fix IE7 error in playground.