Fixed broken scrolling on iOS11 + other improvements

Fixed broken scrolling on iOS11 + other improvements.

👍🏼 @neoneye 👍🏼

Minor improvements.

• Added margin around the StackView
• XCode updates.

Added new methods for scrolling.

For library :

• Added scrollToItem(index: Int) method for library.
• Added scrollToTop and scrollToBottom methods.

For example project :

• updated project for new properties.

Bug fixes and Example update.

Bug fixes and Example update. Added IBDesignable & IBInspectable for storyboard