README: ZLSwipeableViewDelegate -> ZLSwipeableViewDataSource

In the README, `ZLSwipeableViewDataSource` was accidentally referred to as `ZLSwipeableViewDelegate`.
Consistent code style in README.
Removed unnecessary files and made code style a bit more consistent.
Merge pull request #5 from mdznr/master

README: ZLSwipeableViewDelegate -> ZLSwipeableViewDataSource