NewsstandKit Changes

NewsstandKit

Added NSURLConnection.newsstandAssetDownload

Modified NKAssetDownload

	Introduction
From	iOS 8.0
To	iOS 5.0

Modified NKIssue

	Introduction
From	iOS 8.0
To	iOS 5.0

Modified NKIssueContentStatus [enum]

	Introduction
From	iOS 8.0
To	iOS 5.0

Modified NKLibrary

	Introduction
From	iOS 8.0
To	iOS 5.0

Modified NKIssueDownloadCompletedNotification

	Introduction
From	iOS 8.0
To	iOS 5.0