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- rename class with prefix, `DCTitleScrollViewCell` to `DCScrollViewTitleCell`
- bundle `DCScrollViewDelegate`'s methods, to `sizeOfDCScrollViewTitleCell`
- rename delegate and datasource's methods
- update README
update DCScrollView
- rename class with prefix, `DCBodyScrollView` to `DCScrollViewContentView`
- rename class with prefix, `DCTitleScrollView` to `DCScrollViewNavigationView`
code formatter

- bugfix set backgroundView's frame when replacing `sizeOfDCScrollViewTitleCell`
- move sample project's directory, `Demo` to `Example`
- add UnitTest project